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THE SOUL OF THE FAR EAST. i6mo, gilt 

top, $1.25. 
CHOSON: THE LAND OF THE MORNING 

CALM. A Sketch of Korea. Illustrated. 4to, 

gilt top, $5.00; half calf, I9.00; tree calf, $12.00. 
Library Edition. 8vo, gilt top, f 3. 00; half calf, 

$6.00. 
NOTO: AN UNEXPLORED CORNER OF 

JAPAN. i6mo, gilt top, 11.25. 
OCCULT JAPAN: THE WAY OF THE GODS. 

Illustrated. Crown 8vo, $1.75. 

HOUGHTON, MIFFLIN AND COMPANY, 
Boston and New York. 



MARS 



BY 



/ 



PERCIVAL LOWELL 

FELLOW AMERICAN ACADEMY*, MEMBER ROYAL ASIATIC SOCIETY 
GREAT BRITAIN AND IRELAND, ETC. 





BOSTON AND NEW YORK 
HOUGHTON, MIFFLIN AND COMPANY 

1895 



> 



/ 






Copyright, 1895, 
By PERCIVAL LOWELL. 

Ml rights reserved. 



The Riverside Press, Cambridge, Mass., U. S. A. 
Electrotyped and Printed by H. O. Houghton Si Ca 



/ 



9^5 



S^ 



TO 

PROFESSOR WILLIAM EDWARD STORY 

SOMETIME AT FLAGSTAFF HIMSELF 

THIS NEWS FROM A NEIGHBOR 

IS INSCRIBED 



PEEFACE 

This book is the result of a special study of 
the planet made during the last opposition, at 
an observatory put up for the purpose of get- 
ting as good air as practicable, at Flagstaif, 
Arizona. A steady atmosphere is essential to 
the study of planetary detail : size of instru- 
ment being a very secondary matter. A large 
instrument in poor air will not begin to show 
what a smaller one in good air will. When this 
is recognized, as it eventually will be, it will be- 
come the fashion to put up observatories where 
they may see rather than be seen. 

Next to atmosphere comes systematic study. 
Of the extent to which this was realized at 
Flagstaff, I need only say that the planet was 
observed there from May 24, 1894, to April 3, 
1895, during which time, to mention nothing 
else, 917 drawings and sketches were made of 
it. Prof. W. H. Pickering and Mr. A. E. 



VI PREFACE 

Douglass were associated with me in the ob- 
servations herein described. 

Such as care to see the original data more 
technically and minutely treated will find them 
in the first volume of the Annals of this obser- 
vatory. 

Lowell Observatory, 

November, 1895. 



CONTENTS 

CHAFTEB PAGE 

I. General Characteristics 1 

1. As a Star 1 

2. Orbit 8 

3. Size and Shape 14^ 

II. Atmosphere 31 

1. Evidence of it 31 

2. Clouds 60 

III. Water 76 

1. The Polar Cap . . . . . .76 

2. Areography 92 

3. Seas 107 

IV. Canals . 129 

1. First Appearances 129 

2. Map and Catalogue 141 

3. Artificiality 148 

4. Development 154 

V. Oases 176 

1. Spots in the Light Regions .... 176 

2. Double Canals 188 

3. Spots in the Dark Regions .... 197 

VI. Conclusion . . . 201 

Appendix . . 213 

Index 223 



LIST OF ILLUSTRATIONS 

PLATE PAGK 

I. Mars, Sinus Titanum . Colored Frontispiece. 
November, 1894. (P. L.) 

Orbits of Mars and the Earth . . .11 
HuYGHENs' Drawing of the Syrtis Major . 21 
November 28, 1659. 

{From Flammarion's " La Planete Mars.'') 

Terminator Effects 38 

(P. L.) 
II. Map of the South Pole of Mars . . .84 
Showing the Polar Cap and its Changes in 1894. 

(P. L.) 

III. Mars, Longitude 0° on the Meridian . . 96 

(P. Z.) 

IV. Mars, Longitude 30° on the Meridian . . 97 

(P. L.) 
V. Mars, Longitude 60° on the Meridian . . 99 

(P. L.) 
VI. Mars, Longitude 90° on the Meridian . . 100 

(P. L.) 
VII. Mars, Longitude 120° on the Meridian . 101 

(P. L.) 
VIII. Mars, Longitude 150° on the Meridian . . 102 

(P. L.) 
IX. Mars, Longitude 180° on the Meridian . . 103 

(P. Z.) 
X. Mars, Longitude 210° on the Meridian . . 104 

(P. Z.) 
XI. Mars, Longitude 240° on the Meridian . . 105 

(P. Z.) 



viii LIST OF ILLUSTRATIONS 

XII. Mars, Longitude 270° on the Meridian . . 105 

(P. L.) 

XIII. Mars, Longitude 300° on the Meridian . . 106 

(P. i.) 

XIV. Mars, Longitude 330° on the Meridian . . 107 

(P. Z.) 

XV. Syrtis Major Ill 

Showing Seasonal Change during 1894. (P. i.) 

XVI. Hesperia 116 

Showing Seasonal Change during 1894. (P. i.) 

XVII. Sea of the Sirens 122 

Showing Seasonal Change during 1894. (P. Z.) 

XVIII. Fastigium Aryn 138 

October, 1894. (P. L.) 

XIX. Lagus Phoenicis 162 

November, 1894. (P. L.) 

XX. Terminator Views 170 

August 24, 1894. {W. H. P.) 

XXI. Drawings after Opposition (except one) . 171 

{A. E. D.) 
XXII. Drawings after Opposition .... 173 

{A. E. D.) 

XXIII. Phison and Euphrates 194 

Both Double, November 18, 1894. (P. L.) 

XXIV. Mars, on Mercator's Projection . . . 218 

(P. i.) 



MARS 



I 

GENERAL CHARACTERISTICS 
I. AS A STAK 

Once in about every fifteen years a startling 
visitant makes his appearance upon our mid- 
night skies, — a great red star that rises at sun- 
set through the haze about the eastern horizon, 
and then, mounting higher with the deepening 
night, blazes forth against the dark background 
of space with a splendor that outshines Sirius 
and rivals the giant Jupiter himself. Startling 
for its size, the stranger looks the more fateful 
for being a fiery red. Small wonder that by 
many folk it is taken for a portent. Certainly, 
no one who had not followed in their courses 
what the Greeks so picturesquely called " the 
wanderers " (ol TtXavstoc) would recognize in 
the apparition an orderly member of our own 
solar family. Nevertheless, one of the wander- 
ers it is, for that star is the planet Mars, large 
because for the moment near, having in due 
course again been overtaken by the Earth, in 



2 MARS 

her swifter circling about the Sun, at that point 
in space where his orbit and hers make their 
closest approach. 

Although the apparent new-comer is neither 
new nor intrinsically great, he possesses for us 
an interest out of all proportion to his size or 
his relative importance in the universe ; and 
this for two reasons : first, because he is of our 
own cosmic kin ; and secondly, because no other 
heavenly body, Venus and the Moon alone ex- 
cepted, ever approaches us so near. What is 
more, we see him at such times better than we 
ever do Venus, for the latter, contrary to what 
her name might lead one to expect, keeps her- 
self so constantly cloaked in cloud that we are 
permitted only the most meagre peeps at her 
actual surface ; while Mars, on the other hand, 
lets us see him as he is, no cloud-veil of his, as 
a rule, hiding him from view. He thus offers 
us effective opportunities for study at closer 
range than does any other body in the uni- 
verse except the Moon. And the Moon balks 
inquiry at the outset. For that body, from 
which we might hope to learn much, appears 
upon inspection to be, cosmically speaking, 
dead. Upon her silent surface next to nothing 
now takes place save for the possible crumbling 
in of a crater wall. For all practical purposes 
Mars is our nearest neighbor in space. Of all 
the orbs about us, therefore, he holds out most 



AS A STAR 3 

promise of response to that question which man 
instinctively makes as he gazes up at the stars : 
What goes on upon all those distant globes ? 
Are they worlds, or are they mere masses of 
matter ? Are physical forces alone at work 
there, or has evolution begotten something 
more complex, something not unakin to what 
we know on Earth as life ? It is in this that 
lies the peculiar interest of Mars. 

That just as there are other masses of matter 
than our globe, so there are among them other 
worlds than ours is an instant and inevitable 
inference from what we see about us. That we 
are the only part of the cosmos possessing what 
we are pleased to call mind is so earth-centred 
a supposition, that it recalls the other earth- 
centred view once so devoutly held, that our 
little globe was the point about which the 
whole company of heaven was good enough 
to turn. Indeed, there was much more reason 
to think that then, than to think this now, for 
there was at least the appearance of turning, 
whereas there is no indication that we are sole 
denizens of all we survey, and every inference 
that we are not. 

That we are in some wise kin to all the rest 
of the cosmos, science has been steadil}^ demon- 
strating more and more clearly. The essential 
oneness of the universe is the goal to which all 
learning tends. Just as Newton proved all the 



4 MARS 

planets to obey a common force, the Sun ; just 
as Laplace showed it to be probable that we 
were all evolved from one and the same primal 
nebula ; so more recently the spectroscope has 
revealed unsuspected relationship betwixt us 
and the stars. Matter turns out to be but com- 
mon property; and the very same substances 
with which we are so familiar on the Earth, iron, 
magnesium, sodium, and so forth, prove present 
on those far-off suns that strew the depths of 
space. Only in detail does everything differ. 

So much for matter. As for that manifesta- 
tion of it known as mind, modesty, if not intel- 
ligence, forbids the thought that we are sole 
thinkers in all we see. Indeed, we seldom stop 
in our locally engrossing pursuits to realize how 
small the part we play in the universal drama. 
Let ns consider for a moment how we should 
appear, or, more exactly, not appear, could we 
get off our world and scan it from without. If 
distance could thus reduce for us the scale upon 
which the universe is fashioned to one we could 
take in, that on which the Earth should be rep- 
resented by a good-sized pea, with a grain of 
mustard seed, the Moon, circling about it at a 
distance of seven inches, the Sun would be a 
globe two feet in diameter, two hundred and 
fifteen feet away. Mars, a much smaller pea, 
would circle around the two-foot globe three 
hundred and twenty-five feet from its surface ; 



AS A STAR 6 

Jupiter, an orange, at a distance of a fifth of a 
mile ; Saturn, a small orange, at two fifths of 
a mile ; and Uranus and Neptune, good-sized 
plums, three quarters of a mile and a mile and 
a quarter away, respectively. On this same 
scale the nearest star would lie eight thousand 
miles off, and an average third-magnitude star 
at about the present distance of our Moon ; that 
is, on a scale upon which the Moon should be 
but seven inches off, the average star would 
still be as far from us as the Moon is now. 
Now when we think that each of these stars 
is probably the centre of a solar system grander 
than our own, we cannot seriously take our- 
selves to be the only minds in it all. 

Probable, however, as extra-terrestrial life in 
general is, it is another matter to predicate it 
in any particular case. Nevertheless, if it exist 
it must exist somewhere, and the first place to 
scan is the place we can scan best. Now the 
Moon appears to be hopelessly dead. Mars, 
therefore, becomes of peculiar interest, and it 
was in hope of learning something on the sub- 
ject that the observations about to be described 
in this book were made. Before proceeding, 
however, to an account of what in consequence 
we have learned about our neighbor, a couple 
of misapprehensions upon the subject, — not 
confined, I am sorry to say, wholly to the lay 
mind, — must first be corrected. One of these is 



6 MARS 

that extra-terrestrial life means extra-terrestrial 
human life. Such an inference recalls to my 
mind the exclamation of an innocent globe- 
trotter to a friend of mine in Japan once, a 
connoisseur of Japanese painting, upon being 
told that the Japanese pictures were exceed- 
ingly fine. "What!" the globe-trotter ex- 
claimed in surprise, " do the Japanese have pic- 
tures, — real pictures, I mean, in gilt frames?" 
The existence of extra-terrestrial life does not 
involve " real life in trousers," or any other 
particular form of it with which we are locally 
conversant. Under changed conditions, life it- 
self must take on other forms. 

The next point is as to what constitutes 
proof. Now, between the truths we take for 
granted because of their age, and those we 
question because of their youth, we are apt to 
forget that in both proof is nothing but prepon- 
derance of probability. The law of gravitation, 
for example, than which we believe nothing to 
be more true, depends eventually, as recognized 
by us, upon a question of probability ; and so 
do the thousand and one problems of daily life 
upon so many of which we act unhesitatingly 
and should be philosophic fools if we did not. 
All deduction rests ultimately upon the data 
derived from experience. This is the tortoise 
that supports our conception of the cosmos. 
For us, therefore, the point at issue in any 



AS A STAR 7 

theory is not whether there be a possibility of 
its being false, but whether there be a proba- 
bility of its being true. This, which is evident 
enough when squarely envisaged, is too often 
lost sight of in discussing theories on their road 
to recognition. Negative evidence is no evi- 
dence at all, and the possibility that a thing 
might be otherwise, no proof whatever that it 
is not so. The test of a theory is, first, that it 
shall not be directly contradicted by any facts, 
and secondly, that the probabilities in its favor 
shall be sufficiently great. 

As to what constitutes sufficiency it is impor- 
tant to bear in mind one point in the doctrine 
of probabilities, namely, that the chance that 
two or more unrelated events will occur simul- 
taneously is not the sum of the chances that 
each separately occurs, but the product of these 
chances. Therefore, if the probability in favor 
of a theory, in consequence of its explaining a 
certain set of details,' be three to one, and be- 
cause of its explaining another set, — for the 
purposes of argument unrelated to the first, — 
four to one, then the probability in its favor 
from its explaining both sets is not seven to 
one but twelve to one. If it explain a third 
set with an independently resulting probability 
of five to one, the chances in its favor become, 
from its explaining all three sets, not twelve to 
one but sixty to one ; if a fourth set be added, 



8 MARS 

of a probability of five to one, the sum total 
from the four becomes not seventeen to one 
but three hundred to one in favor of its beinp^ 
true. It will be seen how rapidly the proba- 
bility of the truth of a theory mounts up from 
the amount of detail it explains. This law is to 
be remembered throughout the coming exposi- 
tion, for whatever the cogency of each detail of 
the argument in itself, the concurrence of all 
renders them not simply additionally but multi- 
plicitly effective. That different lines of induc- 
tion all converge to one point proves that point 
to be the radiant point of the result. 

II. ORBIT 

To determine whether a planet be the abode 
of life in the least resembling that with which 
we are acquainted, two questions about it must 
be answered in turn : first, are its physical con- 
ditions such as render it, in our general sense, 
habitable ; and secondly, are there any signs of 
its actual habitation ? These problems must be 
attacked in their order, for unless we can 
answer the first satisfactorily, it were largely 
futile to seek for evidence of the second. 

Thoroughly to appreciate, then, the physical 
condition of Mars, we must begin at the begin- 
ning of our knowledge of the planet, since every 
detail will be found to play its part in the final 
result. I shall therefore give in a word or two 



ORBIT 9 

the general facts known about the planet, before 
taking up the observations which make the sub- 
ject matter of this book. The first of these 
general facts is the path the planet describes 
about the Sun. Who first found out that the 
ruddy star we call Mars was not like the rest of 
the company about him we do not know ; possi- 
bly some, to fame unknown, Chaldean shepherd 
alone with the night upon the great Chaldean 
plains. With the stars for sole companions 
while his sheep slept, he must, as he watched 
them night after night, have early recognized 
that they always kept the same configuration. 
They rose and set, but they all rose and set to- 
gether. But one night he thought he noticed 
that one of them had changed its place with 
reference to the rest. A few nights later he 
became sure of it. One of the immovable had 
patently moved. That memorable though un- 
remembered night marked the birth of our 
acquaintance with the rest of the universe. 

Whether the midnight pioneer was Chaldean 
or Assyrian or of some other race, certain it 
is that to the Egyptians we owe the first sys- 
tematic study of the motions of this and of four 
other roving stars, and to the Greeks whom they 
taught, the name by which we know them, that 
of planets, meaning merely wanderers. Since 
then, as we know, many others of like habit 
have been added to the list. 



10 MARS 

Now, from observations of the apparent places 
of a planet, it is possible to determine the rela- 
tive path of the planet in space as compared 
with the path of the Earth. This Kepler did 
from observations of Tycho Brahe's, and showed 
the wanderers to belong to a system of bodies, 
all revolving about the Sun in various elliptic 
orbits, the Sun being at the focus of each ellipse. 
He also found that the line connecting each 
planet with the Sun passed over equal areas in 
equal times, and thirdly, that the times of their 
revolutions were as the cubes of the major axes 
of their orbits. From these three "laws" New- 
ton deduced the fact that the force controlling 
the planets was directed toward the Sun, that 
it varied inversely as the square of the distance, 
and that it was the same in origin for all. This 
is the so-called law of gravitation, and this is 
the way in which it was discovered. We do 
not yet know why gravity so acts, but it is in- 
teresting to note that it follows the simple law 
of geometrical expansion, diminishing in exact 
ratio to the space it fills, just like electricity or 
light. It may, therefore, also be a wave mo- 
tion. 

Thus all the wanderers proved to be asso- 
ciated in common dependence on the Sun, and 
among the members of the solar family thus 
recognized Mars was found to hold the position 
next exterior to the Earth, and the path he fol- 



ORBIT 



11 



lowed in his circuit of the Sun to be situated 
with regard to the Earth's as in the following 
diagram. 



Autumnal Equinox of MARS 
Southern Hemisphere 



Nov.1,1894 

.^VvoA Oct.20.1804 

Oct.1.1894 




Vernal Equinox of MARS Southern Hemlspliere 
270° 



Diagram of the Orbits of Mars and the Earth. 

On consulting the diagram we shall at once 
perceive why it is that every fifteen years Mars 
becomes so unusually bright as to seem, to one 
who has not kept track of him, a new and start- 
ling star. His orbit, it will be seen, is an ellipse 
of some eccentricity, and deviates in conse- 
quence considerably from a circle. The point 
marked Perihelion denotes the point where the 
planet is nearest the Sun; the point marked 



12 MARS 

Aphelion, the point where the planet is the 
most remote from the Sun. In like manner 
the points marked Perihelion and Aphelion on 
the inner circle show the corresponding points 
of the Earth's orbit, which is much more nearly 
circular. Now as the two planets revolve in 
different periods of time, Mars taking 686.98 of 
our days to complete his circuit, and the Earth 
365.26 days to complete hers, the one planet 
will overtake the other only once every two 
years and two months or so. Meanwhile they 
are at great distances apart. But even when 
they do meet, they do not always meet equally 
near. For the one orbital period is not an ex- 
act multiple of the other, and as the orbits are 
both ellipses, it is evident that these meetings 
of the two planets will occur at different points 
of their orbits, and, therefore, at different dis- 
tances. If the meeting occur when Mars is in 
perihelion the planets approach one another 
within 35,050,000 miles ; if in aphelion, only 
within 61,000,000 miles. 

But even this difference in distance does not 
measure the full extent of the variation in bril- 
liancy. As the brightness of an illuminated 
body varies inversely as the square of its dis- 
tance from the source of light, and as the total 
amount of light it reflects to an observer varies 
inversely as the square of his distance from it, 
it makes every difference in the apparent bril- 



ORBIT 13 

liancy of a body how the body is situated, both 
with regard to the source of Hght and with 
regard to the observer. Now it so chances that 
at the meetings of Mars with the Earth these 
two factors attain their maximum effects nearly 
together, and similarly with their minimum. 
For at the times when we are closest to Mars, 
Mars is nearly at his closest to the Sun, and 
reversely when we meet him at the opposite 
part of his orbit. It thus comes about that at 
some meetings, — oppositions, they are called, 
because Mars then is in the opposite part of the 
sky from the Sun, — the planet appears four 
and one half times as bright as at others. Here, 
then, we have the explanation of the planet's 
great changes in appearance, changes so great 
as to deceive any one who has not followed its 
wanderings, into the belief that it is some new 
and portentous apparition. 

Important as is the ellipse in which Mars 
moves with regard to his visibility by us, it 
is considerably more important as regards the 
physical condition of the planet itself. For the 
Sun being situated at one of the foci of his 
orbit, the motion of the planet sweeps him now 
near to, now far from that dispenser of light 
and warmth ; and the amount of both which 
the planet receives varies just like gravity 
with his distance from their source. Now the 
eccentricity of the orbit of Mars is such that 



14 MARS 

when nearest the Sun his distance is 129,- 
600,000 miles, when at his mean distance 
141,500,000 miles, and when most remote 
154,500,000 miles. The proportion of light 
and heat he receives respectively is therefore 
roughly as 16 to 20 to 24 ; or half as much 
again at certain times as at others. 

So much in our knowledge of Mars is pre- 
telescopic. Men might have and practically 
did learn this much without ever seeing the 
planet other than as a point of light. Its orbit 
was tolerably accurately known and could have 
been known still more accurately without tele- 
scopic aid ; not so, until we become much more 
nearly omniscient than we at present are, the 
planet's self. 

III. SIZE AND SHAPE 

With the telescope we enter upon a new 
phase in our knowledge of the planet : the de- 
termination of its shape and size. 

The relative plan of the solar system can be 
learned with great accuracy from observations 
of the motions of its members; not so easily 
learned is the scale upon which it is con- 
structed. Although the former is intrinsically 
a very complicated, the latter a very simple 
problem, two characteristics of the actual sys- 
tem make it possible to solve the former much 
more nearly than the latter. One of these 



SIZE AND SHAPE 15 

characteristics is the fact that the distances 
between the masses which compose the system 
are very much greater than the dimensions of 
the masses themselves, of quite a higher order 
of magnitude. The diameters of the planets 
are measured by thousands of miles, the dis- 
tances between them by tens of millions. The 
second characteristic consists in the approxi- 
mately spherical shape of the planets them- 
selves, and in the fact that by a mathematical 
consequence of the actual law of gravitation a 
sphere acts upon any outside body as if all its 
mass were concentrated at its centre, a most 
interesting peculiarity not true under many 
other supposable laws. These two facts very 
materially simplify the problem of the motions 
of celestial mechanics. 

But just as the first of these peculiarities 
helps us to comprehension of the relative di- 
mensions of the solar system, so does it hinder 
us in determining its actual dimensions. For 
this determination depends upon a problem in 
celestial' surveying, the finding the distance to 
a body by measuring the angle it subtends from 
the two ends of a base-line. Now, as unfortu- 
nately we cannot get off the earth for the pur- 
pose, our base-line is at most the diameter of 
the earth itself, and as the distance to the other 
body immensely exceeds our own size, the angle 
to be measured becomes so excessively small as 



16 MAKS 

to be very difficult to determine with accuracy. 
Fortunately this is matter chiefly of theoretic 
regret, as we now know the actual sizes to 
within a degree of exactness practically suffi- 
cient for most purposes but perturbations; to 
within about 3^0 part of the whole, so far as 
our ultimate measure is concerned, the distance 
we are off from the Sun. 

A good idea of the method and some appre- 
ciation of the difficulty involved in it can be 
got by considering a precisely similar case, that 
of determining the distance of a spire a mile 
and three fifths away by shutting first one eye 
and then the other and noting the shift of the 
spire against its background. It is needless 
to add that without telescopic aid the deter- 
mination is impossible, and that it is exceeding 
difficult with it. 

Nevertheless, from the distance of the Sun 
determined in this manner, we find from 
measurements of the apparent disk of the 
planet made at Flagstaff that Mars is about 
4,215 miles in diameter. This makes his sur- 
face a little more than a quarter that of the 
Earth and his volume about one seventh of 
hers. 

The next point to find out is his mass, that 
is, the amount of matter he contains. This is 
very easy to determine when a planet has a 
satellite, and very difficult to determine when 



SIZE AND SHAPE IT 

a planet has not. The reason is this : the mass 
of a body is known from the pull it exerts, 
inasmuch as this pull depends, by the law of 
gravitation, upon its mass and the square of 
its distance. If then we know the pull and 
the distance from which it is exerted, we can 
find the mass. Now we gauge the pull from 
its effects in causing some other body to move. 
By measuring, therefore, the motion of this 
other body, we learn the mass of the first one. 
To get this accurately the motion must be large 
enough to admit of satisfactory measurement in 
the first place, and be as uncomplicated with 
motions due to pulls of other bodies as pos- 
sible, in the second. As each body pulls every 
other, and it is only their relative displacement 
we can measure, as we have no foothold in 
space, even the case of only two bodies pre- 
sents difficulties of apportionment. We can 
learn the aggregate mass of the two, but not 
the separate mass of either alone unless it so 
happen that the mass of one is so insignificant 
compared w^ith the other that the mass of that 
other may be taken as the mass of both. Now 
this is substantially realized in the case of the 
solar system. Owing to the greatly dispropor- 
tionate size of primary and secondary bodies in 
it, the great si^ of the Sun as compared with 
that of any of the planets, and the great size 
of the planets as compared with their satellites 



18 MAKS 

(with the exception of the Moon, and she, for- 
tunately, is an only child), the determination of 
the mass of the smaller by measurement of its 
motion about the larger, — as if only the pair 
of bodies under consideration existed, and the 
mass of both were concentrated in the greater 
of the two, — is very nearly exact. In conse- 
quence each planet discloses with some accu- 
racy the mass of the Sun, but tells next to 
nothing about its own mass; and in the same 
way each satellite reveals the mass of its pri- 
mary. The mass of a planet possessing a satel- 
lite is, therefore, easy of determination. Not 
so that of one which travels unattended. The 
only way to obtain its mass is from the pertur- 
bations or disturbing pulls it exerts upon the 
other planets, or upon stray comets from time 
to time, and these disturbances are, by the 
nature of the case, of a much smaller order of 
magnitude, to say nothing of the fact that all 
act coincidently to increased difficulty of disen- 
tanglement. The practical outcome of this in 
the case of Mars was that before his satellites 
were discovered the values obtained for his 
mass ranged all the way from syo^oro to 
2500 000 of the mass of the Sun, or, in other 
words, varied fifty per cent. His insignificant 
satellites, however, and just because they are 
insignificant, have made it possible to learn his 
mass with great exactness. It turns out to 



SIZE AND SHAPE 19 

be 3093500 of that of the Sun, or ^| of that of 
the Earth. 

Knowing his mass, we know his average den- 
sity, since to find it we have but to divide his 
mass by his volume. It proves to be -jVo of 
that of the Earth. We also learn the force of 
gravity at his surface, inasmuch as this is di- 
rectly as his mass and inversely as the square 
of his radius. It comes out j^-q of that of the 
Earth. In consequence, all things there would 
weigh but yoq of their weight on earth ; a man, 
for example, weighing 150 pounds here would 
weigh but 55 pounds if transported to the sur- 
face of Mars, and all na^anual labor would be 
lightened threefold. 

So soon as the planet was scanned telescopi- 
cally, he was seen to present a disk, round at 
times, at other times lacking somewhat of a 
perfect circle, showing like the Moon when two 
days off from full. Such appearance visibly 
demonstrated, first, that he was not a self- 
luminous body, and secondly, that he revolved 
about the Sun outside of the Earth. A glance 
at the diagram of the orbit will make the latter 
point clearer. If we draw a line from the Sun 
to the centre of Mars and pass a plane through 
the planet perpendicular to this line and to the 
plane of his orbit, this plane will divide the 
illumined half of him from the unillumined half. 
If now we draw another line from any point 



20 MAHS 

of the Earth's orbit to Mars' centre, and pass a 
plane similarly perpendicular to that, it will cut 
off the hemisphere we see at any moment from 
the one we do not. As the two lines do not in 
general coincide, it will appear that in certain 
positions, in fact in all but two. Mars must pre- 
sent to us a face partly steeped in daylight, 
partly shrouded in night ; in short, that he 
shows gibbous like the Moon when she is be- 
tween the half and the full. This accounts for 
the look of the drawings made during June, 
1894, in which from a seventh to a sixth of 
the disk is wanting on the left.^ By drawing 
lines from his centre to more than one posi- 
tion occupied by the Earth it will be seen that 
this lacking lune reaches a maximum when the 
Earth as viewed from Mars is at extreme 
elongation from the Sun, and that the amount 
of the phase at such time exactly equals the 
number of degrees of this elongation. For 
example, on the sixteenth of last June the lack- 
ing lune amounted to 47°, that is, the Earth 
was then evening star upon the Martian twi- 
light skies at an angular distance of 47° from 
the Sun, about what Yenus seems to us at her 
extreme elongation. In fact, to Mars we oc- 
cupy much the sarne astronomical position that 
Venus does to us. 

To Huyghens we owe the first really impor- 

1 Plates XV., XVI., XVII. 



SIZE AND SHAPE 



21 




Huyghens' drawing of the 
Syrtis Major, Nov. 28, 1659, 
7 p. M. Keproduced from 
Flammarion's " La Planete 
Mars." 



tant telescopic observation upon the planet. On 
November 28, 1659, at 7 s 

p. M., he made the first 
drawing of the planet 
worthy the name, for on 
it is the first identifiable 
feature ever made out by 
man on the surface of 
Mars. This feature is the 
Hourglass Sea, now more 
commonly known as the 
Syrtis Major. The ac- 
companying cut of it is 
reproduced from Flam- 
marion. If the dark patch in it be compared 
with the markings in the other pictures of the 
planet, shown later in this book, it will be seen 
that the patch can be none other than the 
Hourglass Sea. 

Now, innocent as it looks of much detail, 
Huyghens' drawing is perhaps the most im- 
portant one of Mars that has ever been made. 
For, from his observations of the spot it depicts 
at successive dates, he was able to prove that 
Mars rotated on his own axis, and to determine 
the time of that rotation, about 24 hours. As 
he subsequently came to doubt his results, the 
honor of the discovery rests with Cassini, who, 
in 1666, definitely determined that the planet 
rotated in 24 hours 40 minutes. Thus was it 



22 MARS 

first learned that Mars had a day, and that its 
length was not far from the length of our own. 

The importance of these earliest pictures of 
Mars has not lapsed with the lapse of time. By 
comparison of this and other early drawings 
with modern ones, has been deduced a very 
accurate value of the length of the Martian 
day (its sidereal day), a determination accurate 
to the tenth of a second. It amounts to 24 
hours, 37 minutes, 22.7 seconds. Our sidereal 
day, that is, the day reckoned by the stars, not 
by the Sun, is roughly 23 hours, 56 minutes; 
so that the Martian day is about 40 minutes 
longer than our own. The result is not given 
here closer than the tenth of a second, because 
the Flagstaff observations have shown that the 
value of the length of the Martian day hitherto 
accepted is probably a trifle too small. 

From the discovery of the rotation followed 
the approximate position of the planet's poles. 
Eound about the poles so determined appeared 
two white patches, the first study of which we 
owe to Maraldi. They are the planet's polar 
caps. They are to be detected with the smallest 
modern telescope. 

The apparent position of the planet poles as 
presented to the Earth gives the tilt of the 
planet's axis to the plane of its orbit. It turns 
out to be about 25°. This is very nearly the 
same as the Earth's axial tilt to the plane of 



SIZE AND SHAPE 23 

her orbit, which is 23° 24'. As the indination 
of the axis to the plane of the orbit determines 
the seasons, we see that not only has Mars its 
spring, summer, autumn, and winter, but that 
these are not very unlike our own. 

It is not uninteresting to inquire in what the 
difference consists. The slight difTerence of tilt 
in the Martian axis would slightly extend the 
breadth of the tropical and the polar regions at 
the expense of the temperate ones, and thus 
accentuate the seasons, but the chief seasonal 
contrast between Mars and the Earth would 
come in in consequence of the much greater 
eccentricity of Mars' orbit. For the more ec- 
centric the ellipse, the greater the variation in 
the planet's velocity at different parts of it, in- 
asmuch as the Sun pulls the planet toward him- 
self with a force depending on his distance. 
The less this distance, the greater the angular 
velocity. But the angular velocity determines 
the length of the seasons upon a planet whose 
pole of rotation is tilted to the plane of its 
orbit, like the Earth or Mars. The greater the 
eccentricity of the ellipse, therefore, the greater 
the difference in the length of the seasons. In 
the case of the Earth the difference is about 
eight days, winter in the northern hemisphere 
being eight days shorter than summer. In the 
case of Mars, owing to the much greater eccen- 
tricity of his orbit combined with his longer 



24 MARS 

period, the difference amounts to 74 days. In 
one hemisphere winter is long and cold, sum- 
mer short and hot ; in the other winter and 
summer interchange. Owing to the present 
position of the line of apsides, the line connect- 
ing the points of Mars' nearest approach to and 
farthest recession from the Sun, the former 
hemisphere happens to be the southern one ; 
the latter, the northern. The lengths of their 
respective seasons are as follows : — 

In the northern hemisphere, winter lasts 147 
of his own days; spring, 191 days; summer, 
181 days ; autumn, 149 days ; while in the 
southern hemisphere, winter lasts 181 days; 
spring, 149 days ; summer, 147 days ; autumn, 
191 days. 

Curiously enough, an analogous distribution 
of heat and cold occurs also at the present time 
in the case of the Earth ; its axis and line of 
apsides holding the same relation to each other 
that the Martian ones do. This similarity of 
aspect is, as we shall see later, apparently very 
curiously reproduced in certain peculiarities of 
the surfaces of the two planets. But with Mars 
the result is much more marked on account 
of the greater eccentricity of his orbit, which 
is .0931 as against the Earth's .0168. 

As even under these exaggerated conditions 
his two polar regions show much alike, modern 
theories about our glacial epochs are consider- 
ably shaken. 



SIZE AND SHAPE 25 

The last of the preliminary points to be taken 
up is the form of the planet. Consideration of 
it makes in some sort a bridge from the planet's 
past to its present. For its deviation from a 
perfect sphere tells us something of its history. 

Between the shapes of the large planets, 
Jupiter, Saturn, Uranus, and probably Neptune, 
and those of the small ones. Mercury, Venus, 
the Earth, and Mars, there is a striking dis- 
similarity, the former being markedly oblate 
spheroids, the latter almost perfect spheres. 

Into the cause of this, very interesting as it 
is, we have not here space to go. The effect, 
however, is so noticeable that while the most 
casual glance at the disk of Jupiter will reveal 
its ellipticity, the most careful scrutiny would 
fail to show Mars other than perfectly round. 

Nevertheless, the planet is slightly flattened 
at the poles. Measures have repeatedly been 
made to determine the extent of this flattening, 
with surprisingly discordant results, most of the 
values being much too large. 

Observations at Flagstaff during this last op- 
position have not only shown that most of the 
values w^ere too large, but have revealed the 
cause of their discrepancy. There turns out to 
be a factor in the case, hitherto unsuspected, 
whose presence proves to be precisely such as 
would cause the observed variations in measure- 
ments. It not only accounts for the fact of 



26 MARS 

discrepancy, but for the further fact that the 
discrepancies should usually be on the side of 
an increase of the apparent polar flattening. 
This factor is the recognition of a perceptible 
twilight upon the planet, not only of enough 
account to be visible, but to have been actually 
measured, quite unconsciously, by Mr. Douglass, 
and disclosed only when the measures came to 
be compared with each other. Of this I shall 
speak more at length when we reach the sub- 
ject of atmosphere. Here it is only necessary 
to say that the presence of a twilight fringing 
the surface of the planet would have the effect 
of increasing the apparent size of the equatorial 
diameter at all times, but to a different degree 
at different times, and almost always more than 
it would the polar one. In consequence, the 
polar flattening, which is the ratio borne by the 
difference of the equatorial and polar diameters 
to the equatorial diameter, would be seemingly 
increased. 

The value of Mr. Douglass' measures is height- 
ened by a certain happy event of an unprece- 
dented nature, — the first observed disappear- 
ance of the polar cap, and that at the very 
time the most important measures were made. 
The presence of the polar cap enters as a dis- 
turbing element into measures of the planet's 
disk, on account of the increased irradiation it 
causes at the extremity of the polar diameter, 



SIZE AND SHAPE 27 

wliicli makes the polar diameter measure more 
than it otherwise would. For the polar cap is 
the most brilliant part of the disk ; and for the 
same reason that any bright body seems larger 
than a dark one of the same size, it dilates the 
planet unduly in that direction. The resulting 
effect is further complicated by the fact that 
the polar cap is eccentrically situated with re- 
gard to the pole of rotation, as we shall see 
later ; and as the pole is tilted, the cap is some- 
times on the edge of the disk and the irradia- 
tion in consequence large, and sometimes well 
on the disk itself where its irradiation is little 
or nothing. As the amount of its magnifying 
effect is not accurately known, there enters with 
it an unknown error. Now, last autumn Nature 
herself kindly eliminated this source of error. 

The measures made by Mr. Douglass are thus 
entitled to special regard, not only because of 
their number (a great many of them were 
taken), but chiefly because Nature made the 
disturbing influence of the polar cap nil. When, 
in addition, the twilight arc is allowed for, the 
measures show a most satisfactory accordance 
and give for the value of the polar flattening 
1^0 of the equatorial diameter. 

Now, it is interesting that this value should 
receive corroborative support from two quite 
different directions. The first of these is that 
1^ is just about the flattening which would re- 



28 MARS 

suit from the most probable supposition we can 
make as to the past history of the planet. To 
show this we may take the case of the Earth. 
Investigations along several different lines all 
result in showing that the polar flattening of 
the Earth is almost exactly such as would re- 
sult in a fluid body whose density from surface 
to centre increased according to the pressure 
and temperature of our Earth in the past, and 
which rotated with its present angular velocity. 
In the case of Mars, Tisserand has shown that 
the polar flattening under the influence of his 
present rotation would, if the increase of den- 
sity in his strata were similar to the Earth's, 
be sJy C)f his equatorial diameter. If, on the 
other hand, his mass were homogeneous, his 
polar flattening would be jj-g. Now, in a fluid 
condition a body could not remain homogene- 
ous, owing to the pressure exerted by the outer 
strata upon the inner ones, unless the matter of 
which it was composed were rigorously incom- 
pressible, which is certainly not the case with 
the Earth, and with quite equal certainty not 
the case with Mars. On the other hand, the 
increase of density from surface to centre is un- 
doubtedly less in Mars than in the Earth, since 
the pressure depends upon the mass and the 
Earth's mass is nearly ten times that of Mars. 
Consequently, from this cause, the polar flatten- 
ing should be somewhere between jjs ^^^ 22T? 



SIZE AND SHAPE 29 

not far therefore from the value found above, 



1, 

19' 



The second bit of corroborative testimony 
comes from the behavior of the satellites of the 
planet. Unlike a sphere, a spheroid acts un- 
equally upon a body revolving about it, not in 
the plane of its equator. The ring of matter 
pulls the satellite now this way, now that, thus 
altering its nodes, that is, the points where 
the plane of its orbit crosses the planet's equa- 
tor, and also its apsides, or the points in 
which the satellite's orbit is nearest and farthest 
from the planet. The effect of an equatorial 
protuberance tilted thus is to shift these points 
round the orbit, the line of nodes retrograding, 
while the line of apsides usually advances. 
From the speed with which these revolutions 
take place, it is possible to calculate the size of 
the bulge. Hermann Struve has just done this 
for the lines of apsides of the two satellites of 
Mars, and finds for the value for the consequent 
polar flattening of the planet i^o <^f its equa- 
torial diameter. From these two independent 
determinations we may conclude that the value 
found at Flagstaff is pretty nearly correct. 

We find, then, that Mars is a little flatter 
than our Earth, though not noticeably so, the 
polar flattening amounting to about 22 miles. 

The value, j^, for his polar flattening, hints 
that at some past time Mars was in a fluid — 



30 MARS 

that iSj a molten — condition, just as the Earth's 
polar flattening of 3^3 similarly shows her to 
have been, and that in both cases the flatten- 
ing was then impressed. Now, inasmuch as the 
tides, lunar and solar in the case of the Earth, 
solar practically alone in the case of Mars, have 
been slowing up the planet's rotation ever since 
this refrigeration happened, but as their respec- 
tive rates of rotation still agree substantially 
with what a fluid condition demands, it is evi- 
dent that in the case of neither planet could 
the cooling have begun so very long ago, but 
that it began longer ago for Mars than for the 
Earth. 

In so far, then, we trace a certain similarity 
of development in the early chaotic stage of 
evolution of the two planets, a stage pre-natal 
to their career as worlds. 

From these basic facts of size and shape we 
will now go on to more latter-day detail. 



n 

ATMOSPHERE 
I. EVIDENCE OF IT 

To all forms of life of which we have any 
conception, two things in nature are vital, air 
and water. A planet must possess these two 
requisites to be able to support any life at all 
upon its surface. For there is no creature, no 
plant, no anything endowed with the possi- 
bility of that kind of change we call life, which 
is not in some measure dependent upon both of 
them. How, then, is Mars off for air ? 

Fortunately for an answer to this question, 
air, in the post-chaotic part of a planet's career, 
plays as vital a role in the inorganic processes 
of nature as in the organic ones. By the post- 
chaotic period of a planet's history we may des- 
ignate that time in its evolutionary existence 
which follows the parting with its own inherent 
heat. After its heat has gone from it, atmos- 
phere becomes essential, not only to any form 
of life upon its surface, but to the production of 
any change whatever there. Without atmos- 
phere all development, even the development 



32 MARS 

of decay, must come to a stand-still, when once 
what was friable had crumbled to pieces under 
the alternate roasting and refrigerating, rela- 
tively speaking, to which the body's surface 
would be exposed as it turned round on its axis 
into and out of the Sun's rays. Such disinte- 
gration once accomplished, the planet would roll 
thenceforth a mummy world through space. 

An instance of this death in life we have ex- 
emplified by the nearest of the heavenly bodies, 
our own Moon. That cataclysmic changes once 
occurred there is still legible on her face, while 
the present well-nigh complete immutability of 
that face shows that next to nothing happens 
there now. Except for the possible tumbling 
in of a crater wall, such as seems to have taken 
place in the case of Linne a few years ago, all 
is now deathly still. But atmosphere is as ab- 
sent as change. Whatever it may have had in 
the past, there is at present no perceptible air 
upon the surface of the Moon. And change 
'pro tanto knows it no more. 

With Mars it is otherwise. Over the surface 
of that planet changes do occur, changes upon a 
scale vast enough to be visible from the Earth. 
To appreciate the character and extent of these 
changes we will begin with the appearance of 
the planet last June.^ From the drawings it 
will be seen that the general aspect of the 

1 Plates v., VI., VII. Uppermost figure. 



ATMOSPHERE 33 

planet's surface at that time was tripartite. 
Upon the top part of the disk, round what we 
know to be the planet's pole, appeared to be a 
great white cap. This was the planet's south 
polar cap. The south lay at the top, because 
all astronomical views are, for optical reasons, 
upside down; but, inasmuch as we never see 
the features otherwise, to have them right side 
up is not vital to the effect. Below the white 
cap lay a region chiefly bluish-green, inter- 
spersed, however, with portions more or less 
reddish-ochre. Below this, again, came a vast 
reddish-ochre stretch. 

The first sign of change occurred in the polar 
cap. It proceeded slowly to dwindle in size. 
Such self-obliteration it has, with praiseworthy 
regularity, been seen to undergo once every 
two years since it was first seen by man. For 
nearly two hundred years now, it has been 
observed to wax and wane with clock-like pre- 
cision, a precision timed to the change of sea- 
son in the planet's year. During the spring, 
these snow-fields, as analogy at once guesses 
them to be, and as beyond doubt they really 
are, stretch in the southern hemisphere, the 
one presented to us at this last opposition, down 
to latitude sixty-five south and even further, 
covering thus more than the whole of the 
planet's frigid zone. As summer comes on, 
they dwindle gradually away, till by early au- 



34 MAES 

tumn they present but tiny patches a few hun- 
dred miles across. This year, for the first time 
in human experience, they melted, apparently, 
completely. 

The history of the cap's vicissitudes we shall 
take up farther on in connection with the ques- 
tion of water. It is only necessary here to note 
that changes occurred in it. 

The disappearance of the polar snows is by 
no means the only change discernible upon the 
surface of the planet. Several years ago Schia- 
parelli noticed differences in tint at successive 
oppositions both in the dark areas and in the 
bright ones. These, he suggested, might be 
due to seasons. At the last opposition, that of 
1894, it was possible at Flagstaff, owing to the 
length of time the planet was kept under ob- 
servation, to watch the changes occur; thus 
conclusively proving them to be changes of a 
seasonal character. 

From early in June, which corresponded to 
the Martian last of April, to the end of Novem- 
ber, which corresponded to the Martian last of 
August, the bluish-green areas underwent a 
marked transformation. During the summer 
of the Martian southern hemisphere, a wave of 
seasonal change swept down from the pole over 
the face of the planet. What and why it was 
we will examine in detail when we take up the 
question of water. Like the changes in the 



ATMOSPHERE 35 

polar cap, it suffices here to chronicle the fact 
that it took place ; for the fact of its occurjrence 
constitutes proof positive of the presence of an 
atmosphere. 

A moment's consideration will show how ab- 
solutely positive this proof is. It is the inevi- 
table deduction from the simplest of observed 
facts. Its cogency gains from its very sim- 
plicity. For it is independent of difficult detail 
or of doubtful interpretation. It is not con- 
cerned with what may be the constitution of 
the polar caps, nor with the character of the 
transformation that sweeps, wave-like, over the 
rest of the planet's face. It merely takes note 
that change occurs, and that note is final. 

Now, since this was originally written, certain 
observations made at this observatory by Mr. 
Douglass have resulted apparently, most unex- 
pectedly, in actually revealing this atmosphere 
to sight. Although the existence of an atmos- 
phere is absolutely established by the above 
considerations, it is interesting to have ocular 
demonstration of it to boot ; and this the more, 
that it would not have been thought possible to 
detect what, so to speak, disclosed itself. For 
the discovery was quite unconsciously made, 
being of the nature of a by-product to the 
outcome of another investigation. So syste- 
matically was his general search conducted that 
when the results came to be worked out it 



36 MARS 

appeared not only that he had seen an atmos- 
phere, but actually measured it, although he 
was quite unaware of doing so at the time. 
The occasion was the measuring of the diame- 
ters of the planet, polar and equatorial. Micro- 
metric measures of these were begun as early 
as the beginning of July, and kept up at inter- 
vals till the latter part of November. But the 
ones that proved specially tell-tale were those 
made from September 20th to November 22d, 
a set of polar and a set of equatorial ones hav- 
ing been taken throughout that interval on 
twenty-six nights. 

Now, when these measures came to be worked 
out by me, corrected for all known sources of 
error and reduced to distance unity, a curi- 
ous result made its appearance. As they 
stood arranged in their table chronologically, 
it was at once evident, even before taking the 
means, that, as time went on, something had 
affected the equatorial diameter which had 
not affected the polar one. 

The values for the polar diameter were nearly 
the same from first to last. The equatorial 
values, on the other hand, showed, apparently, 
a systematic increase as the eye followed down 
the column. Something, therefore, had been 
at work on the one, which had not been at 
work on the other. Almost as instantaneously, 
it was evident what this something was, to wit. 



ATMOSPHERE 37 

a visible twilight unconsciously measured for a 
part of the planet's surface. Like the .Down- 
easter who shingled fifty feet on to the fog, 
Mr. Douglass had measured several miles into 
the Martian air. 

A word or two will explain this. The planet 
came to opposition on October 20. The first 
measures of the series, therefore, were taken 
within a few days of opposition, just before and 
just after that event. The subsequent ones, 
on the other hand, were made at a gradually 
increasing distance from this position, as the 
planet passed toward quadrature. Now, at op- 
position, the disk of the planet is full, like the 
full Moon ; while, as it passes to quadrature, it 
loses something of itself, becoming gibbous, as 
the Moon does two or three days after the full. 
This loss from phase chiefly affects the equa- 
torial diameter, the polar one remaining sub- 
stantially unchanged by it. It would remain 
absolutely unchanged if the planet moved in 
the plane of the ecliptic. It does not so move, 
but the quantity resulting from lack of accord- 
ance is so small that for the present explana- 
tion it may be neglected. Now, this question 
of phase was the only point, practically, in which 
the equatorial and polar diameters differed dur- 
ing the interval under consideration. This, 
then, was the clew to the discrepancy. 

It was not, however, the loss of phase that 



38 



MAES 



was in question. That would have decreased 
the values of the equatorial diameter instead of 
increasing thera, and, what is more immediately 
to the point, the correction for it had already 
been made. This correction is easily ascer- 
tained, for it depends chiefly upon the position 
of the planet in its orbit, which is known with 
great accuracy. The * resulting values, there- 
fore, had nothing to do with the phase correc- 
tion as such, but they did, nevertheless, have 
to do with the phase itself. 



Earth 

{3d position) 



Sun Throughout 




ATMOSPHERE 39 

To see exactly how this is possible, let us 
consider the effect an illuminated atmosphere 
would have upon the measurements in ques- 
tion. To make matters more obvious we will 
introduce a diagram. The inner circle repre- 
sents a section of the planet in the plane of the 
ecliptic ; the arrows, the directions in the same 
plane of the Sun and Earth from the centre of 
the planet, in the different positions to be con- 
sidered ; and the outer circle, an atmosphere 
surrounding the planet, at the limit at which 
it is dense enough to reflect light. 

At opposition the Earth lay very nearly in 
the same line from the planet as the Sun. This 
is shown by the left-hand arrow. The illumi- 
nated semi-circumference of the planet's surface, 
at that time also the semi- circumference seen 
from the Earth, was gcibp, and gop was the 
equatorial diameter ; g'dVp' and g'opl the semi- 
circumference and equatorial diameter, upon 
the supposition of an atmospheric envelope en- 
circling the surface. As the Earth and Mars 
passed along their orbits, the line from Mars 
to the Earth shifted into its second position, 
the Sun remaining- as before. The illuminated 
part of the surface of Mars continued, there- 
fore, to be gcibp ; but the portion of this illumi- 
nated surface visible from the Earth was only 
dhp, the part gd being invisible from the Earth, 
and the part ph lying in shadow. If, however, 



40 MARS 

there were an atmosphere capable of reflecting 
light up to a height represented by the greater 
circle, the Sun's rays would strike the upper 
visible limit of this atmosphere, not at j) but at 
s, ST being drawn parallel to the line from o to 
the Sun. The measured equatorial diameter, 
which is, of course, the projection of the arc 
dVs on the line d!li ^ would be d!f instead of c?e, 
which it would be were there no atmosphere. 
It thus appears that owing to side-lengthening, 
as we may perhaps style this reverse of fore- 
shortening, the fringe of atmosphere increases 
in apparent width with increase of phase, to an 
apparent increase of the equatorial diameter. 

If, now, we take a third position for the Earth 
where Mars shows a yet greater phase, the third 
arrow, we find that in this case the resulting 
apparent increase in the equatorial diameter is 
m?i, and we notice that mn is greater than e/", 
just as ef was greater than jyp' or qg . That is, 
we see that the apparent increase in the size of 
the equatorial diameter varies directly, accord- 
ing to some law, with the increase in phase, or, 
as it is technically put, is a function of the 
phase. 

This increase, being an increase in the meas- 
ure itself, would in due course come in for its 
share of all the corrections applied to the diame- 
ter. In consequence, that diameter, instead of 
coming out simply the full equatorial diameter, 



ATMOSPHEKE 41 

would come out too big in proportion to the 
amount added by the twilight arc. 

Pursuant, therefore, to the supposition that 
such was the cause of the increase, I took the 
means of the polar and of the equatorial diame- 
ters with regard to the time from opposition, at 
which the measures were made, to find myself 
confronted by a series of values counterparting 
what we have just seen would be given by the 
presence of a visible twilight arc. The result- 
ing values are : — 

Polar Diameters : 

October 15 to 23 inc. 9''.35 

October 12 and 24 to 30 inc. r.35 
November 2 to 21 inc. 9'^36 

Equatorial Diameters : 

October 15 to 23 inc. r.40 

October 12 and 24 to 30 inc. r.43 
November 2 to 21 inc. 9''. 51 

The measure of the 12th of October and 
those of the 24th to 30th are taken together, 
because equidistant from opposition on Octo- 
ber 20. 

The agreement of this table with that de- 
ducible by theory from the effect of an atmos- 
phere is striking. But the agreement is even 
more exact than appears. For, as the polar 
axis was not in the same line as the axis of 
phase, the twilight arc to some extent affected 
the polar diameter at all times, but specially 



42 MARS 

during November. This becomes evident, nu- 
merically, on applying the correction for an 
atmosphere, which gives the following values : 
Polar Diameters : 

October 15 to 23 inc. 9^32 

October 12 and 24 to 30 inc. r.31 
November 2 to 21 inc. ^.32 

Equatorial Diameters : 

October 15 to 23 inc. 9''.37 

October 12 and 24 to 30 inc. 9''.36 
November 2 to 21 inc. 9''.37 

The middle values are evidently somewhat 
too small, since they affect both the polar and 
equatorial diameters alike. Otherwise the varia- 
tion in the values of the same diameter is less 
than the probable errors of observation. Tak- 
ing the mean of all but the middle ones, we 
deduce the value for the polar flattening given 
above, j^-q of the equatorial diameter. 

From the correction for the effect of the at- 
mosphere, we find the amount of the twilight 
arc upon the planet visible from the Earth to 
be about 10°. That of the Earth, as seen from 
the Earth's surface, is 18° ; but it is to be no- 
ticed that here the point of view is important. 
From the topmost layer of our air of sufficient 
density to be capable of reflecting light we are 
but forty miles away ; from the corresponding 
layer of the Martian air we are forty millions 
of miles off. We cannot, therefore, expect to 



ATMOSPHERE 43 

detect the one to the same extent that we can 
the other. The value, then, for the Martian 
twihght arc of 10° is simply a minimal value, 
not an absolute one. The twilight arc cannot, 
from the observations, be less than this, but it 
may be much more. 

The large number of measures from which 
the above means were deduced not only ren- 
ders error in the result less likely, but shows 
that result to be due to air pure and simple. 
This appears from the fact that the observed 
increase is systematic. For its systematic char- 
acter proves it due to something largely trans- 
parent. It is because it is chiefly not seen that 
it is seen at all. At first sight this deduction 
seems paradoxically surprising. But, in consid- 
ering the problem, we shall realize that it must 
be so. 

If what was seen were opaque, as, for ex- 
ample, a mountain, then in certain positions it 
would indeed be seen projecting beyond the 
terminator, — for example, if it were at s in 
the diagram on page 38 ; if, on the other hand, 
it were in the position r, it would, instead of 
apparently increasing, decrease the diameter. 
Now, as the rotation of the planet would bring 
it eventually into all possible positions, it would 
be as likely on any one occasion to be measured 
in a position to decrease the diameter as to 
increase it. From but a few measures, there- 



44 MARS 

fore, it might appear that there was an in- 
crease in the calculated diameter, or it might 
seem that there was a decrease from it, and 
either would be equally likely to happen. If, 
however, many measures were made, and just 
in proportion as they were many, those decreas- 
ing the diameter would offset those increasing 
it, and the mean of all would show no trace of 
either. In the mean the minus quantity would 
wipe out the plus. Indeed, owing to the fact 
that both the Sun and the Earth are not infi- 
nitely far off from Mars, and in consequence 
that all the lines to them are not strictly par- 
allel to one another, the decreasing effect would 
actually slightly exceed the increasing effect, 
but this would be too small to be perceptible. 

The same argument that applies to moun- 
tains applies to clouds, or to any opaque sub- 
stance. Sporadic increase might be due to 
them ; but for the increase to be systematic, 
it is necessary that the substance seen should 
also be seen through. It must be in part trans- 
parent. The measures, therefore, not only dis- 
close the presence of an atmosphere, but do so 
directly. 

Having thus seen first with the brain and 
then with the eye, and both in the simplest 
possible manner, that a Martian atmosphere 
exists, we will go on to consider what it may 
be like. 



ATMOSPHERE 45 

The first and most conspicuous of its char- 
acteristics is cloudlessness. A cloud is an event 
on Mars, a rare and unusual phenomenon, which 
should make it more fittingly appreciated there 
than Ruskin lamented was the case on Earth, 
for it is almost perpetually fine weather on our 
neighbor in space. From the day's beginning 
to its close, and from one end of the year to 
the other, nothing appears to veil the greater 
part of the planet's surface. 

This would seem to be even more completely 
the case than has hitherto been supposed. We 
read sometimes in astronomical books and arti- 
cles picturesque accounts of clouds and mists 
gathering over certain regions of the disk, hid- 
ing the coast-lines and continents from view, and 
then, some hours later, clearing off again. Very 
possibly this takes place, but not with the cer- 
tainty imputed to it. It is also doubtful if 
certain effects of longer duration are really 
attributable to such cause. For closer study 
reveals another cause at work, as we shall see 
later, and the better our own air the more the 
Martian skies seem to clear. Certainly no in- 
stance of the blotting out of detail upon the 
surface of Mars has been seen this year at 
Flagstaff. Though the planet's face has been 
scanned there almost every night, from the last 
day of May to the end of November, not a 
single case of undoubted obscuration of any 



46 MARS 

part of the central portions of the planet, from 
any Martian cause, has been detected by any 
one of three observers. Certain peculiar bright- 
ish patches have from time to time been noted, 
but, with a courtesy uncommon in clouds, they 
have carefully refrained from obscuring in the 
slightest degree any feature the observer might 
be engaged in looking at. 

The only certain dimming of detail upon the 
Martian disk has been along its bright semi- 
circular edge or edges, as the case may be, — 
what is technically called its limb. Fringing 
this is a permanent lune of light that swamps all 
except the very darkest markings in its glare. 
This limb-light has commonly been taken as 
evidence of sunrise or sunset mists on Mars. 
But observations at Flagstaff during last June 
show that such cannot be the case. In June 
Mars was gibbous, — that is, he showed a face 
like the Moon between the quarter and the 
full, — and along his limb, then upon his own 
western side, lay the bright limb-light, stretch- 
ing inward about thirty degrees. Since the face 
turned toward us was only in part illumined by 
the Sun, the centre of it did not stand at noon, 
but some hours later, and the middle of the 
limb consequently not at sunrise, but at about 
nine o'clock of a Martian morning. As the 
limb-light extended in from this thirty degrees, 
or two hours in time, the mist, if mist it was, 



ATMOSPHERE 47 

must have lasted till eleven o'clock in the day. 
Furthermore, it must have been mist of a sin- 
gularly mathematical turn of mind, for it 
stretched from one pole to the other, quite 
oblivious of the fact that every hour from sun- 
rise to sunset lay represented along the limb, 
including high noon. What is more, as the disk 
passed, in course of time, from the gibbous form 
to the full, and then to the gibbous form on the 
other side, the limb-light obligingly clung to 
the limb, regardless of everything except its 
geometric curve. But as it did so, the eleven 
o'clock meridian swung across it from one side 
of the disk to the other. As it passed the 
centre the regions there showed perfectly clear ; 
not a trace of obscuration visible as it lay be- 
neath the observer's eye. 

From the first observation it is evident that 
Martian sunrise and sunset had nothing to do 
with the phenomenon, since it was not either 
Martian sunrise or sunset at the spot where it 
was seen ; and, from both observations taken 
together, it is evident that the phenomenon did 
have to do with the position of the observer. 
For nothing on Mars had changed in the mean 
time, but only the point of view of the observer 
on Earth. It is clear, therefore, that it was not 
a case of Martian diurnal meteorological change, 
but a case of foreshortening of some sort. 

To what, then, was the limb-light due ? At 



48 MARS 

first sight, it would seem as if the Moon might 
help us ; for the Moon's rim is similarly ringed 
by a lune of light. In her case the effect has 
been attributed to mountain slopes holding the 
Sun's light at angles beyond the possibility of 
plains. But Mars has few mountains worthy 
the name. His terminator — that is, the part 
of the disk which is just passing in or out of 
sunlight, and discloses mountains by the way in 
which they catch the coming light before the 
plains at their feet are illuminated — shows 
irregularities quite inferior to the lunar ones, 
proving that his elevations and depressions are 
relatively insignificant. 

Not due, then, to either mountains or mist, 
there is something we know that would produce 
the effect we see, — dust or water particles in 
the Martian air ; that is, just as the Earth's 
atmosphere is somewhat of a veil, so is the 
Martian one, and this veiling effect, though 
practically imperceptible in the centre of the 
disk, becomes noticeable as we pass from the 
centre to the edge, owing to the greater thick- 
ness of the stratum through which we look. 
At thirty degrees from the edge, our line of 
sight pierces twice as much of it as when we 
look plumb down upon the centre of the disk, 
and more yet as we approach the edge itself ; 
in consequence, what would be diaphanous at 
the centre might well seem opaque toward the 



ATMOSPHERE 49 

limb. The effect we are familiar with on Earth 
in the haze that always borders the horizon, — 
a haze most noticeable in places where there is 
dust, or ice, or water in the air. Here, then, 
we have a hint of the state of things on Mars. 
Ice particles both are probable and would give 
the brilliancy required. 

This first hint receives independent support 
from another Martian phenomenon. Contrary 
to what the distance of the planet from the 
Sun and the thinness of its atmospheric en- 
velope would lead us to expect, the climate of 
Mars appears to be astonishingly mild. Whereas 
calculation from distance and atmospheric den- 
sity would put its average temperature below 
freezing, thus relegating it to perpetual ice, the 
planet's surface features imply that the tem- 
perature is relatively high. Observation gives 
every evidence that the mean temperature 
must actually be above that of the Earth ; for 
not only is there practically no sign of snow or 
ice outside the frigid zone at any time, but the 
polar snow-caps melt to a minimum quite be- 
yond that of our own, affording rare chance 
for quixotic polar expeditions. Such pleasing 
amelioration of the climate must be accounted 
for, and aqueous vapor seems the most likely 
thing to do it ; for aqueous vapor is quite spe- 
cific as a planetary comforter, being the very 
best of blankets. It acts, indeed, like the glass 



60 MARS 

of a conservatory^ letting the light-rays in and 
opposing the passage of the heat-rays out. 

The state of things thus disclosed by observa- 
tion, the cloudlessness and the rim of limb-light, 
turns out to agree in a most happy manner 
with what probability would lead us to expect ; 
for the most natural supposition to make a 
priori about the Martian atmosphere is the fol- 
lowing : When each planet was produced by 
fission from the parent nebula, we may suppose 
that it took with it as its birthright its propor- 
tion of chemical constituents; that is, that its 
amount of oxygen, nitrogen and so forth was 
proportional to its mass. Doubtless its place in 
the primal nebula would to a certain extent 
modify the ratio, just as the size of the planet 
would to a certain extent modify the relative 
amount of these elements that would thereupon 
enter into combination. Supposing, however, 
that the ratio of the free gases to the other 
elements remained substantially the same, we 
should have in the case of any two planets the 
same relative quantity of atmosphere. But the 
size of the planet would entirely alter the dis- 
tribution of this air. 

Three causes would all combine to rob the 
smaller planet of efficient covering, on the gen- 
eral principle that he that hath little shall have 
less. 

In the first place, the smaller the planet the 



ATMOSPHERE 51 

greater would be its volume in proportion to 
its mass, because the materials of which it was 
composed, being subjected to less pressure 
owing to a lesser pull, would not be crowded 
so closely together. This is one reason why 
Mars should have a thinner atmosphere than 
our Earth. 

Secondly, of two similar bodies, spheres or 
others, the smaller has the greater surface for 
its volume, since the one quantity is of two 
dimensions only, the other of three. An onion 
will give us a good instance of this. By strip- 
ping off layer after layer we reach eventually 
a last layer which is all surface, inclosing no- 
thing. We may, if we please, observe something 
analogous in men, among whom the most super- 
ficial contain the least. In consequence of this 
principle, the atmosphere of the smaller body 
finds itself obliged to cover relatively more sur- 
face, which still further thins it out. 

Lastly, gravity being less on the surface of 
the smaller body, the atmosphere is less com- 
pressed, and, being a gas, seizes that opportunity 
to spread out to a greater height, which renders 
it still less dense at the planet's surface. 

Thus, for three reasons. Mars should have a 
thinner air at his surface than is found on the 
surface of the Earth. 

Calculating the effect of the above causes 
numerically we find that on this a priori sup- 



52 MARS 

position Mars would have at his surface an at- 
mosphere of about fourteen hundredths, or one 
seventh, of the density of our terrestrial one. 

Observation supports this general supposi- 
tion ; for the cloudless character of the Martian 
skies is precisely what we should look for in a 
rare air. Clouds are congeries of globules of 
water or particles of ice buoyed up by the air 
about them. The smaller these are, the more 
easily are they buoyed up, because gravity, 
which tends to pull them down, acts upon their 
mass, while the resistance they offer varies as 
the surface they present to the air, and this is 
relatively greater in the smaller particles. The 
result is that the smaller particles can float in 
thinner air. We see the principle exemplified 
in our terrestrial clouds ; the low nimbus being 
formed of comparatively large globules, while 
the high cirrus is made up of very minute par- 
ticles. If we go yet higher, we reach a region 
incapable of supporting clouds of any kind, so 
rarefied is its air. This occurs about five miles 
above the Earth's surface ; and yet even at this 
height the density of our air is greater than is 
the probable density of the air at the surface of 
Mars. We see, therefore, that the Martian at- 
mosphere should from its rarity prove cloudless, 
just as we observe it to be. 

So far in this our investigation of the Martian 
atmosphere we have been indebted solely to the 



ATMOSPHERE 53 

principles of mathematics and molar physics for 
help, and these have told us something about 
the probable quantity of that atmosphere, 
though silent as to its possible quality. On 
this latter point, however, molecular physics 
turns out to have something to say ; for an 
Irish gentleman. Dr. Gr. Johnstone Stoney, has 
recently made an ingenious deduction from the 
kinetic theory of gases bearing upon the atmos- 
pheric envelope which any planet can retain. 
His deduction is as acute as it appears from ob- 
servation to be in keeping with the facts. It 
is this : — 

The molecular theory of gases supposes them 
to be made up of myriads of molecules in inces- 
sant motion. What a molecule may be nobody 
knows ; some scientists supposing it to be a 
vortex ring in miniature, — something like the 
swirl made by a teaspoon drawn through a cup 
of tea. But, whatever it be, the idea of it 
accounts very creditably for the facts. The 
motion of the molecules is almost inconceivably 
swift as they dart hither and thither through- 
out the space occupied by the gas, and their 
speed differs for different gases. From the ob- 
served relations of the volumes and weights of 
gases to the pressures to which they are sub- 
jected is deduced the fact of this speed and 
its amount. It appears that the molecules of 
oxygen travel, on the average, at the rate of 



54 MARS 

fifteen miles a minute ; and those of hydrogen, 
which are the fastest known, at the enormous 
speed of more than a mile a second. But this 
average velocity may, for any particular mole- 
cule, be increased by collisions with its neigh- 
bors. The maximum speed it may thus attain 
Clerk-Maxwell deduced from the doctrine of 
chances to be sevenfold the averao-e. What 
may thus happen to one, must eventually hap- 
pen to all. Sooner or later, on the doctrine of 
chances, each molecule of the gas is bound to 
attain this maximum velocity of its kind. When 
it is attained, the molecule of oxygen travels at 
the rate of one and eight tenths miles a second, 
the molecule of water vapor at the rate of two 
and one half miles a second, and the molecule 
of hydrogen at over seven miles a second, or 
four hundred and fifty times as fast as our fast- 
est express train. 

Now, if a body, whether it be a molecule 
or a cannon-ball, be projected away from the 
Earth's surface, the Earth will at once try to 
pull it down again : this instinctive holding 
on of Mother Earth to what she has we call 
gravity. In the cases with which we are per- 
sonally familiar, her endeavor is eminently suc- 
cessful, what goes up coming down again. But 
even the Earth is not omnipotent. As the 
velocity with which the body is projected in- 
creases, longer and longer time is needed for 



ATMOSPHERE 55 

the Earth to overcome it and compel the body's 
return. Finally there would be reached a speed 
which the Earth would just be able to overcome 
if she took an infinite time about it. In that 
case the body would continue to travel away 
from her, at a constantly diminishing rate, but 
still at some rate, on and on into the depths of 
space, if there were no other bodies in the uni- 
verse but the Earth and the molecule, till it 
attained infinity, at which point the truant 
would stop, and then reluctantly return. This 
velocity we may call the critical velocity. It 
is also known as the parabolic velocity, because 
it is at any point the velocity of a body mov- 
ing in a parabola about the Earth, under the 
Earth's attraction ; the parabola being the curve 
of a fall from infinity. The critical velocity is 
the parabolic velocity, inasmuch as gravity is 
able to destroy on the way up just the speed it 
is able to impart on the way down. But, now, 
if the body's departure were even hastier than 
this, the Earth would never be able wholly to 
annihilate its speed, and the body would travel 
out and out forever. If its speed at starting 
were less than twenty-seven miles a second, it 
would become thenceforth a satellite of the 
Sun ; if its speed were yet greater, it would 
become an independent rover through space, 
paying brief visits only to star after star. In 
any case the Earth would know the vagabond 
no more. 



56 MARS 

As gravity depends upon mass, the larger the 
attracting planet the greater is its critical ve- 
locity, the velocity it can just control ; and, 
reversely, the smaller the planet the less its 
restraining power. With the Earth the critical 
velocity is six and nine tenths miles a second. 
If any of us, therefore, could manage to acquire 
a speed greater than this, socially or otherwise, 
we could bid defiance to the whole Earth, and 
begin to voyage on our own account through 
space.-^ 

This speed is actually attained, as we have 
seen, by the molecules of hydrogen. If, there- 
fore, a molecule of free hydrogen were present 
at the surface of the Earth, and met with no 
other gas attractive enough to tie it down by 
uniting with it, the rover would, in course of 
time, attain a speed sufficient to allow it to bid 
good-by to Earth, and start on interspacial 
travels of its own. That it should reach its 
maximum speed is all that is essential to lib- 
erty, the direction of its motion being immate- 
rial. To molecule after molecule would come 
this happy dispatch, till the Earth stood de- 
prived of every atom of free hydrogen. 

Now, it is a highly significant fact that there 
is no free hydrogen found in the Earth's atmos- 
phere. There is plenty of it in the captivity 
of chemical combination, but none in the free 

1 See Appendix. 



ATMOSPHERE 57 

state. This coincidence of lack of hydrogen 
with lack of liberty takes on yet more signifi- 
cance from the fm^ther fact that the same is not 
true of oxygen, water vapor, or indeed of any 
of the other gases we know. With them, free- 
dom is not synonymous with absence. The 
Earth's atmosphere contains plenty of free oxy- 
gen, nitrogen, and the like. But, as we have 
just seen,^ the maximum speed of all these gases 
falls short of the possibility of escape. This 
accoimts for their presence. They have stayed 
with us solely because they must. 

The appearance of the other heavenly bodies 
seems to confirm this conclusion. The Moon, 
for example, possesses no atmosphere, and cal- 
culation shows that the velocity it can control 
falls short of the maximum of any of our atmos- 
pheric gases, that velocity being but one and 
one half miles a second. All were, therefore, 
at liberty to leave it, and all have promptly 
done so. On the other hand, the giant planets 
give evidence of very dense atmospheres. They 
have kept all they ever had. 

But the most striking confirmation of the 
theory comes from the cusps of Yenus and 
Mercury; for an atmosphere would prolong, 
by its refraction, the cusps of a crescent beyond 
their true limits. Length of cusp becomes, con- 
sequently, a criterion of the presence of an at- 

^ See Appendix. 



58 MARS 

mospliere. Now, in the appearance of their 
cusps there is a notable difference between 
Venus and Mercury. The cusps of Venus ex- 
tend beyond the semi-circle ; Mercury's do not. 
We see, therefore, that Mercury has apparently 
little or no atmospheric envelope, and we find 
that his critical velocity is only 2.2 miles per 
second, — below that of water vapor, and peril- 
ously near that of nitrogen and oxygen. 

Turning to the case of Mars, we find with 
him the critical velocity to be three and one 
tenths miles a second. Now, curiously enough, 
this is, like the Earth's, below the maximum 
for the molecules of hydrogen, but also, like 
the Earth's, above that of any other gas ; from 
which we have reason to suppose that, except 
for possible chemical combinations, his atmos- 
phere is in quality not very unlike our own. 

Having seen what the atmosphere of Mars is 
probably like, we may draw certain interesting 
inferences from it as to its capabilities for mak- 
ing life comfortable. The first consequence of 
it is that Mars is blissfully destitute of weather. 
Unlike New England, which has more than it 
can accommodate. Mars has none of the article. 
What takes its place there, as the staple topic 
of conversation for empty-headed folk, remains 
one of the Martian mysteries yet to be solved. 
What takes its place in fact is a perpetual 
serenity such as we can scarcely conceive of. 



ATMOSPHERE 59 

Although over what we shall later see to be 
the great continental deserts the air must at 
midday be highly rarefied, and cause vacuums 
into which the surrounding air must rush, the 
actual difference of gradient, owing to the initial 
thinness of the air, must be very slight. With 
a normal barometer of four and a half inches, 
a very great relative fall is a very slight actual 
one. In consequence, storms would be such 
mild-mannered things that, for objectionable 
purposes, they might as well not be. In the 
first place, there can be but little rain, or hail, 
or snow, for the particles would be likely to 
be deposited before they gained the dignity of 
such separate existence. Dew or frost would 
be the common precipitation on Mars. The 
polar snow-cap or ice-cap, therefore, is doubt- 
less formed, not by the falling of snow, but by 
successive depositions of dew. Secondly, there 
would be about the Martian storms no very 
palpable wind. Though the gale might blow 
at fairly respectable rates, so flimsy is the sub- 
stance moved that it might buffet a man un- 
mercifully without reproach. 

Another interesting result of the rarity of 
the air would be its effect upon the boiling- 
point of water. Reynault's experiments have 
shown that, in air at a density yo^ of our own, 
water would boil at about 127° Fahrenheit. 
This, then, would be the temperature at which 



60 MARS 

water would be converted into steam on Mars. 
So low a boiling-point would raise the relative 
amount of aqueous vapor held in suspension by 
the air at any temperature. At about 127° the 
air would be saturated, and even at lower tem- 
peratures much more of it would evaporate and 
load the surrounding air than happens at similar 
temperatures on Earth. Thus at the heels of 
similarity treads contrast. 

We may now go on to some phenomena of 
the Martian atmosphere of a more specific char- 
acter. 

II. CLOUDS 

Although no case of obscuration has been 
seen at Flagstaff this summer, certain parts of 
the planet's disk have appeared unaccountably 
bright at certain times. That these are not 
storm-clouds, like those which, by a wave-like 
process of generation, travel across the Ameri- 
can continent, for example, is shown by the 
fact that they do not travel, but are local fix- 
tures. Commonly, the same places appear 
bright continuously day after day and recur- 
rently year after year, different astronomers at 
successive oppositions having so observed them. 
To this category belong the regions known as 
Elysium, Ophir, Memnonia, Eridania, and 
Tempe, which at certain seasons of the Martian 
year are phenomenally brilliant. They stay so 
for some time, and then the brightness fades out 



CLOUDS 61 

to appear again at the next opposition. Still 
smaller bright spots, apparently more fugitive, 
have been seen this year by Professor W. H. 
Pickering, notably just north of the Mare Si- 
renum. None of the phenomena look distinc- 
tively like cloud. There are, however, pheno- 
mena that do. 

Toward the end of August there were seen 
several times, first by Professor Pickering and 
then by me, strange flocculent collections of 
white patches, about fifteen degrees from the 
pole, in the place where the snow-cap had been, 
the cap itself having retreated farther south. 
In look they were unlike the snow-cap ; and 
also unlike the land. But they did have very 
much the look of clouds. Possibly they were 
clouds, formed from the vapor left in the air by 
the melting of the cap. It was then but a few 
days to the summer solstice. 

But the most marked instance of variability 
was detected in September last by Mr. Doug- 
lass in the western part of Elysium. On Sep- 
tember 22 and 23 he found this blissfully 
bright region y as usual, equally bright through- 
out. But on September 24 he noticed that 
the western half of it had suddenly increased in 
brightness, and far outshone the eastern half, 
being almost as brilliant as the polar cap. 
When he looked at it again the next night, 
September 25, the effect of the night before 



62 MARS 

had vanished, the western half being now ac- 
tually the darker of the two. So fugitive an 
effect suggests cloud, forming presumably over 
high ground, and subsequently dissipating ; it 
also suggests a deposition of frost, melting on 
the next day. It is specially noteworthy that 
the canals inclosing the region, the Galaxias, the 
Boreas, and the Eunostos, were not in any way 
obscured by the bright apparition. On the con- 
trary, Mr. Douglass found them perceptibly 
darker than they had been, an effect attributable 
perhaps to contrast. 

Although not storm-clouds, it is possible that 
these appearances may have been due to thin 
cloud, capping high land. There are objections 
to this view, but as there are graver ones 
to any other it may stand provisionally, the 
more so that there are appearances not easily 
reconcilable with other cause. For example, a 
most singular phenomenon was seen by Mr. 
Douglass on November 25, a bright detached 
projection, for which, from measurement, he 
deduced a height of thirty miles. This would 
seem to have been cloud, for the details of its 
changes in appearance seem quite incompatible 
with a mountainous character. With regard to 
its enormous height, it is not to be forgotten 
that a few years ago on the Earth phenomenal 
dust-clouds were observed as high as one hun- 
dred miles. 



CLOUDS 63 

We now come to a highly interesting class 
of observations bearing upon the question of 
clouds, — Mr. Douglass's terminator observa- 
tions. During the last opposition, seven hundred 
and thirty-six irregularities upon the terminator 
of the planet were detected at Flagstaff. They 
were seen by one or more of three observers, 
but chiefly by Mr. Douglass, who made a syste- 
matic scrutiny of the terminator for almost 
every degree of Martian longitude. Their full 
presentation would be both too tabular and too 
technical for this book. The paper embodying 
them will be found among the published annals 
of this observatory. I shall here give only cer- 
tain deductions from it. 

Of the 736 irregularities observed, 694 were 
not only recorded but measured. Of these 403 
were depressions. It is singular, in view of 
their easy visibility, that, with the exception 
of Schroeter in the last century, no one should 
have noticed them before. Schroeter, indeed, 
saw two appearances of exactly this sort, — one 
on the 21st of September, 1798, and the other 
on the 12th of November, 1800. Nevertheless 
they are not difficult to see, and anything but 
rare. When the phase is large enough, several 
may be seen every night. 

The projections number 291. As their num- 
ber shows, they are less common than the de- 
pressions, but they are even less of a feature of 



64 MARS 

the surface than their number would indicate, 
for the depressions extend as a rule much fur- 
ther both in latitude and longitude. 

Usually the depressions look like parings from 
the planet's rind, and almost always appear upon 
that part of the terminator where the dark re- 
gions are passing out of sight ; commonly there- 
fore, in the case of the southern hemisphere, 
they are met with between latitudes 30° to 60° 
south. Not so common is it for them to occur 
over a part of the planet which is bright. 
Furthermore, they appear to occur more or less 
continuously. This would not be the case were 
they real depressions. 

As this may not at once be evident to the 
reader, and yet is easily made evident, we will 
consider the diagram on page 38. It will there 
be seen that an elevation like s or r — and the 
same reasoning applies mutatis mutandis to a 
depression — appears projected a relatively long 
way without or within the terminator, as com- 
pared with its actual length, owing to the angles 
under which it is respectively illuminated by 
the Sun and seen from the Earth. The rela- 
tion between its height and its distance from the 
edge is that between the height of a hill and 
the shadow it casts at sunrise or sunset. What, 
therefore, is not high enough to be seen in pro- 
file on the limb, becomes vicariously visible on 
the terminator. But a hill could not continue 



CLOUDS 65 

long to appear as an elevation, as the rotation 
of the planet would carry it in due course from 
the position r to the position s, and there it 
would be forced to masquerade as a depression. 
The same, reversely, would happen to a val- 
ley. In order that a depression should appear 
continuously, there must be a belt of lower 
level along its circle, and this could not be 
made visible as in the former case by projec- 
tion, since projection depends upon difference of 
level along the same surface contour, not as be- 
tween adjacent ones. It could, therefore, only 
be noted by its actual profile, — a very small 
affair, still further diminished by reason of the 
angle under which that profile was viewed. 
The resulting quantity in the case of Mars 
would be exceedingly minute. We perceive 
therefore, on the very threshold of our inquiry, 
reason to doubt the mountainous character of 
the irregularities. Such inference becomes the 
more probable on a more detailed investigation, 
into which we will now enter. This investiga- 
tion depends upon a very important principle ; 
namely, that if we have, as in this case, a great 
number of observations, it is possible, by divid- 
ing them into classes according to their kind and 
then taking the mean value of each class, to 
discover characteristics not otherwise exposed. 

Means are very telling things. They are so 
from the fact of simplifying the effects of the 



QQ MARS 

factors at work. By taking tlie average of the 
series of observed values according to some defi- 
nite principle, not only do we eliminate a very 
large class of errors, but we allow by so doing 
the various causes to unmask their separate 
results. The importance of reasoning upon 
averages could hardly be more strikingly ex- 
emplified than in the very case before us, — that 
of these depressions and projections seen on the 
terminator of Mars. 

Of the 694 irregularities measured, 291 were 
projections and 403 were depressions. Here at 
the very outset, then, we perceive an objection 
to the theory that they are due to mountains ; 
to wit, because the number of depressions so 
greatly exceeds the number of projections. As 
previously explained on page 64, mountains 
would produce on the average as many projec- 
tions as depressions, for they would project the 
light on the one side as much as they would 
cut it off on the other. 

Now let us classify these irregularities, and 
see if we can gain further information about 
them. There were two kinds of them, — the 
long and low, and the short and sharp. Each 
kind had its representatives among both the 
projections and the depressions. Of the short 
and sharp variety there were 95 projections. 
These averaged 0.276 seconds of arc in height. 
Of the same kind there were similarly 57 depres- 



CLOUDS 67 

sions which averaged 0.368 seconds of arc in 
depth. It will be noticed then, first, that the 
projections of this character exceeded in num- 
ber the depressions of the same ; secondly, that 
the average depth of the depressions exceeded 
the average height of the projections. Now, 
if the appearances had been due to mountains, 
both the number and size of the projections 
and of the depressions should have been sub- 
stantially the same. They were emphatically 
neither. Consequently mountains fail to ex- 
plain them. But there is another possible set 
of phenomena that will ; namely, clouds. For, 
in the first place, clouds would cause apparent 
depressions and projections, since the light would 
linger on them as it does on mountain tops, and 
they would cast shadows as mountains do. But 
furthermore their two effects, of extending or 
curtailing the limit of vision along the termina- 
tor, would not necessarily be equal, as would be 
the case with hills. Because it is a peculiarity 
of mountains that they are attached to the soil, 
and are commonly permanencies ; while clouds 
are not. The latter form and dissipate, dissi- 
pate and re-form, and their metamorphoses are 
phenomena depending upon the time of day. 
Consequently they may appear in one place 
at one time, in another the next ; and what is 
no less important, they may form at different 
heights at different times. They therefore not 



68 MAES 

only account for irregularities on the termina- 
tor, but they account also for irregularity in the 
plus or minus character of these irregularities. 
Cloudsj therefore, are capable of explaining the 
case before us, although mountains are not. 

From what we have just shown let us mark 
now just what clouds are here required to ac- 
count for what we see. The clouds that cause 
depressions are those within the terminator, — 
those, that is, that form before sunset o/ after 
sunrise ; while those that cause projections are 
those that gather after sunset or before sun- 
rise. As the observed projections in this 
case exceed the depressions in number, we 
infer, then, that there are more clouds after 
nightfall than before it, and similarly more 
before daybreak than after it ; next, as the 
average depression is greater than the average 
projection, we likewise infer that the day clouds 
lie at a higher altitude. Now, this is precisely 
what we should expect would be the case, just 
as it is the case on the Earth. 

Of the other class of irregularities, the long 
and low, there were observed 196 projections 
and 346 depressions. The jirojections averaged 
0''.136 in height; the depressions, 0'M25 in 
depth. Here, then, we have an opposite state of 
things from that with which we were confronted 
in the short and sharp class. Here, as compared 
with the projections, instead of relatively few 



CLOUDS 69 

depressions of greater height, we have rela- 
tively many depressions of less height. Fur- 
thermore, there are a great many more of both 
projections and depressions than there were of 
the former variety, and they are both of much 
less height or depth. Evidently, therefore, we 
have here, in part at least, a different class of 
phenomena from what we have previously con- 
sidered. Now we perceive at once that two 
factors enter here which did not enter in the 
case of the short and sharp irregularities. The 
long and low depressions occur, as we shall re- 
call, almost always over the dark areas, while 
the short and sharp ones do not. In the next 
place, the average height or depth of the long 
and low irregularities is much nearer the value 
of the irradiation constant, that is, the amount 
by which a bright object seems bigger on ac- 
count of its brightness ; which would cause the 
dark areas to seem depressed. From these facts 
we infer that most of the depressions of this 
class are due to the character, not to the con- 
tour, ol the surface where they occur ; partly to 
the direct effect of lack of irradiation, partly 
to sombreness of the surface, which would cause 
the light to fade from them at a greater relative 
distance from the terminator. On eliminating 
these depressions, therefore, we find ourselves 
left with very few depressions as against nearly 
200 projections. The excess in number of the 



70 MARS 

latter shows, as in the case of the other variety, 
that we are here deahng chiefly with long and 
relatively low clouds formed after sunset or be- 
fore sunrise ; those so formed during daylight 
being few if any. 

One more observation made at Flagstaff, on 
the subject of cloud, is as peculiar as it is 
important. It was made by Mr. Douglass, and 
I shall give it in his own words. A more de- 
tailed account of it, together with his tables of 
figures, will appear in his paper upon it in the 
Observatory annals : — 

" On November 25 and 26 a bright spot was 
seen in the unilluminated portion of Mars, to 
which, in my opinion, no other name than cloud 
can be applied. Its great height, size, and bril- 
liancy, and, on the second evening, its singu- 
lar fluctuations, render it of importance in the 
study of the Martian atmosphere. 

" I first saw it at 16h. 35m., G. M. T., of No- 
vember 25, and made an estimate of its height. 
It seemed to be rapidly increasing in length in 
a direction parallel to the terminator at that 
point. Subsequent estimates of its height gave 
a different and greater value than at first, until 
its sudden disappearance at 17h. 6m., or perhaps 
a minute later. After once attaining its size, it 
seemed to remain with little change, presenting 
the appearance of a line 115 miles long by 33 
miles wide at the centre and lying parallel to 



CLOUDS 71 

the terminator, but separated from it by an ap- 
parent space of over 80 miles. It was gener- 
ally yellowish in color, like the limb, but of less 
brilliancy than the centre of the disk, though 
distinctly surpassing in that respect the adja- 
cent terminator. I estimated it to have the 
brilliancy of the bright areas of the disk at a 
distance of 9° from the terminator. In one 
view it appeared to be a very small whitish 
point, and I am inclined to think that there 
may have been a real diminution in its size at 
that moment. This idea is partly sustained by 
the following night's observations. At 16h. 
54m. it was observed by Professor Pickering, 
whose estimate gave 11 miles for its height. At 
17h. 5m., after obtaining two readings of the 
micrometer screw for latitude, the seeing, which 
had been quite steadily at the figure 7 (on a 
scale of 10), dropped to 4, and in attempt- 
ing the next setting I could not find the 
' cloud,' although once before it had remained 
visible when the seeing dropped instantaneously 
to that figure. Nor did it reappear in the next 
half hour. This sudden disappearance, without 
any previous lessening of its height above the 
terminator or of its size, made its cloud charac- 
ter unmistakable, since a mountain beyond the 
sunrise terminator must either constantly de- 
crease in height, or soon join the illuminated 
disk. 



72 MARS 

" A subsequent computation showed that this 
phenomenon took place over the southern part 
of Schiaparelli's Protei Kegio. Other reasons 
lead me to think, however, that he has placed 
that island some 5° too far south. 

" On November 26 the cloud promptly ap- 
peared at 17h. 15m., G. M. T., but nearly 9° far- 
ther north. Instead of remaining continuously 
Visible, it dissipated and reformed at irregular 
intervals. The first appearance lasted sixteen 
minutes. After somewhat over four minutes 
had passed, it reappeared momentarily, and six 
minutes elapsed before it appeared again, lasting 
then but two and one half minutes. Then fol- 
lowed an absence of three minutes, presence for 
two minutes, absence for three minutes, presence 
for one minute, and a final brief appearance 
eight minutes later at 18h. Im. Its presence 
was suspected five minutes before that hour, 
and again at 18h. 11m., but with great uncer- 
tainty. 

" At this time it presented in general the 
same characteristics as the night before, though 
its appearances were too brief to permit such 
careful observations as were hoped for. The 
seeing, too, was not so good as before, varying 
from 4 to 7 ; and if the cloud happened to ap- 
pear under the former figure, its observation 
was difficult. It is needless to remark that 
under such conditions it was impossible to ob- 



CLOUDS 73 

serve its appearance or disappearance to the 
second. In general, it seemed to exhibit a less 
elevation than the night before. A careful 
estimate of its latitude placed it precisely at the 
centre of the terminator. I believe these lati- 
tude observations, though made rapidly, cannot 
be subject to an error greater than 2°, and prob- 
ably less than 1°. On November 27, at 18h., I 
searched for the cloud, but was not rewarded by 
finding any trace of it. 

'' Estimates of the size and height of this 
cloud were made with reference to a glass 
thread in the micrometer, whose diameter is 
0''.6. One tenth of the thread was found to rep- 
resent on Mars a little less than twenty miles. 
This gives us an elevation above the surface of 
between 10 and 11 miles. In this process we 
have taken the apparent centre of the cloud, 
and have assumed the seeing to have no influ- 
ence. We obtain, therefore, the smallest possi- 
ble mean height of the centre of the cloud. If 
we assume that the seeing was not perfect, its 
eifect would be to lessen the separation, but not 
to change the total height. Supposing, for ex- 
ample, that the apparent extension of the cloud 
was due to poor seeing enlarging a point, then 
our terminator distance would be 245 miles, 
and our minimum elevation 15 miles. There- 
fore we can assume 15 miles to be the smallest 
probable mean elevation of this cloud. The 



74 MARS 

average height of our cirrus clouds is five and 
one half miles. 

'' One more idea requires mention, namely, 
the movement of this cloud in latitude. From 
the extreme rarity of clouds on Mars I am in- 
clined to connect intimately the appearances of 
the two evenings, and consider them as due to 
one source, presumably a large body of air mov- 
ing northward. Such an advance would be at 
the rate of 13.1 miles per hour.'' 

I may add to this that the height of the 
cloud — relatively to those of the Earth — is 
what direct deduction from the less rapid thin- 
ning out of the air above the Martian surface, 
which must result from the smaller mass of 
Mars, would lead us to expect. The air at the 
surface would be thinner than at the surface 
of the Earth, but the rate at which it diminished 
with the height above that surface would not be 
so great. At no very great elevation the two 
densities would come to be the same. 

One deduction from this thin air we must 
be careful not to make — that because it is thin 
it is incapable of supporting intelligent life. 
That beings constituted physically as w^e are 
would find it a most uncomfortable habitat is 
pretty certain. But lungs are not wedded to 
logic, as public speeches show, and there is 
nothing in the world or beyond it to prevent, so 
far as we know, a being with gills, for example, 



CLOUDS 75 

from being a most superior person. A fish doubt- 
less imagines life out of water to be impossible ; 
and similarly to argue that Hfe of an order 
as high as our own, or higher, is impossible 
because of less air to breathe than that to 
which we are locally accustomed, is, as Flamma- 
rion happily expresses it, to argue, not as a 
philosopher, but as a fish. 

To sum up, now, what we know about the 
atmosphere of Mars : we have proof positive 
that Mars has an atmosphere ; we have reason 
to believe this atmosphere to be very thin, — 
thinner at least by half than the air upon the 
summit of the Himalayas, — and in constitution 
not to difier greatly from our own. 



Ill 

WATER 
I. THE POLAR CAP 

After air, water. If Mars be capable of 
supporting life, there must be water upon his 
surface ; for, to all forms of life, water is as vital 
a matter as air. On the question of habitabil- 
ity, therefore, it becomes all-important to know 
whether there be water on Mars. 

To the solution of this inquiry, also, the 
planet's polar cap turns out to hold the key. 
For just as the fact of change in the cap proves 
the presence of air, so the manner of that 
change implies the presence of water. It not 
only does this ; it turns out to do a deal more. 
For to the whole water question it appears to 
play the part not only of occasion but of cause. 
In more senses than one, it is in that great 
glistening white patch that our water problem 
takes its rise. 

On the 3d of June, 1894, the south polar cap 
stretched, almost one unbroken waste of white, 
over about 55 degrees of latitude. A degree 
on Mars measures 37 miles; consequently the 



THE POLAR CAP 77 

cap was 2,035 miles across. Inasmuch as the 
inclination of the Martian equator to the plane 
of the Martian orbit is, according to Schiapa- 
relli, 24° 52', it must have then covered more 
than the whole south frigid zone of the planet. 

Now, to take in the full meaning of the con- 
dition of the cap at this time and of the changes 
that ensued, we must begin by determining the 
Martian time of year. This is done by fixing 
the dates at which the Martian pole reached 
its maximum tilt toward or from the Sun, and 
the dates at which it was not tilted either to 
or from, but sideways to, the Sun ; the former 
gives us the Martian solstices, and the latter 
the Martian equinoxes. It thus appears that 
on April 7, 1894, occurred the vernal equinox 
of the Martian southern hemisphere, on August 
31, its summer solstice, and on February 7, 
1895, its autumnal equinox. From these dates 
it is easy to transform the one calendar into the 
other. On the 3d of June, 1894, therefore, it 
was about May 1 on the southern hemisphere 
of Mars. 

On May 1, then, Martian time, the cap was 
already in rapid process of melting ; and the 
speed with which it proceeded to dwindle 
showed that hundreds of square miles of it were 
disappearing daily. As it melted, a dark band 
appeared surrounding it on all sides. Except, as 
I have since learned, at Arequipa, this band has 



78 MARS 

never, I believe, been distinctively noted or 
commented on before, which is singular, con- 
sidering how conspicuous it was at Flagstaff. 
It is specially remarkable that it should never 
have been remarked upon elsewhere, in that 
a similar one girdling the north polar cap was 
seen by Beer and Madler as far back as 1830. 
For it is, as we shall shortly see, a most signifi- 
cant phenomenon. In the first place, it was the 
darkest marking upon the disk, and was of a 
blue color. It was of different widths at differ- 
ent longitudes, and was especially pronounced 
in tint where it was widest, notably in two 
spots where it expanded into great bays, one in 
longitude 270° and one in longitude 330°. The 
former of these was very striking for its color, 
a deep blue, like some other-world grotto of 
Capri. The band was bounded on the north, 
that is, on the side toward the equator, by the 
bluish-green areas of the disk. It was con- 
trasted with these both in tone and tint. It 
was both darker and more blue. 

The band not only varied in width at differ- 
ent longitudes, but its width corresponded to 
the amount of the blue-green areas of the disk 
visible at these longitudes below it. It was 
widest where these were greatest in extent, and 
narrowest where they were least. If we con- 
sult the map of Mars we shall see that below 
the bay in longitude 330° hes the great dark 



THE POLAR CAP 79 

area, the Syrtis Major, and, below the one in 
longitude 270"^, the Syrtis Minor. This corre- 
lation was highly suggestive in itself. As if, 
however, to remove all question as to possible 
coincidence having a hand in the matter, the 
agreement in position was emphasized by visi- 
ble connection. Two long dark streaks appeared 
joining respectively each bay to its correspond- 
ing Syrtis. 

But the most significant fact about the band 
was that it kept pace with the polar cap's re- 
treat toward the pole. As the white cap shrank 
it followed pari passu so as always to border 
the edge of the snow. It thus showed itself 
not to be a permanent marking of the planet's 
surface, since it changed its place, but a tempo- 
rary one, dependent directly upon the waning 
of the cap itself. In short, it was an associated 
detail, and itself instantly suggested its charac- 
ter, namely, that it was water at the edge of 
the cap due to the melting of the polar snow. 

Not only did the band conform with the cap 
in position; it did so in size. As the snows 
dwindled, the blue band about them shrank in 
width to correspond. By August it was a 
barely discernible thread drawn round the tiny 
white patch which was all that remained of the 
enormous snow-fields of some months before. 
Finally, on October 13, when the snow entirely 
disappeared, as we shall presently see, the spot 



80 MARS 

where it and its girdle, long since grown too 
small for detection, had been became one yellow 
stretch. 

That the blue was water at the edge of the 
melting snow seems unquestionable. That it 
was the color of water ; that it so persistently 
bordered the melting snow ; and that it subse- 
quently vanish edjs^are three facts mutually con- 
firmatory to this deduction. But a fourth bit 
of proof, due to the ingenuity of Professor W. 
H. Pickering, adds its weight to the other three. 
For he made the polariscope tell the same tale. 
On scrutinizing the great bay through an Arago 
polariscope, he found the light coming from the 
bay to be polarized. Now, to polarize the light 
it reflects is a property, as we know, of a smooth 
surface such as that of water is. 

Before going further we will take up here 
at the outset the question of the constitution 
of these polar caps, which in their general be- 
havior so strikingly suggest our own ice-caps as 
they would appear could they be seen from a 
distance of forty millions of miles. That they 
so instantly suggest snow has suggested, to that 
class of mind which likes to make of molehills 
of question mountains of doubt, the possibility 
that instead of ice we have here snow-caps of 
solid carbonic acid gas (carbon dioxide). The 
occasion of the suggestion is the fact that car- 
bonic dioxide under certain conditions becomes 



THE POLAR CAP 81 

a colorless liquid, and then a solid of a floccular, 
snow-like character. It assumes, in short, under 
proper conditions of pressure and cold, the va- 
rious appearances presented by water under 
higher temperatures, although it does so with 
very different degrees of ease. Superficially, 
therefore, the idea seems plausible. Let us see 
if it still seems so when critically examined. 

Faraday made experiments on the relation of 
the congealing point of carbonic acid gas to the 
pressure, and found that at 0° C. it took a pres- 
sure of 36 atmospheres, that is, 540 pounds to 
the square inch, to solidify the gas, and that at 
— 99° C, the lowest temperature with which he 
experimented, it took 1.14 atmospheres. At 
this point the curve representing the relation 
was becoming apparently asymptotic, that is, 
a slight decrease in pressure involved a great 
falling off of temperature. Under a pressure 
of one atmosphere, therefore, the temperature 
would be about — 170° F., that is, on the surface 
of the Earth this would be the congealing point 
of the gas. 

He found further that the curve for the lique- 
faction point lay very close to that for the con- 
gealing point, and approached yet closer as the 
pressure decreased. In other words, the gas 
passed almost immediately from the gaseous to 
the solid state. 

In the light of these facts let us consider the 



82 MARS 

condition of Mars. Three points arise which 
we will take in the inverse order of their im- 
portance. First : the appearance of the planet 
shows conclusively that, if the polar caps be 
composed of solid carbonic acid gas, then either 
there is no water at all on Mars in any form 
whatsoever, or what there is is ice so overlaid 
with detritus as to be invisible. For if the two 
substances were there together, and the cold at 
the surface of the planet of so extreme a char- 
acter as to congeal the carbon dioxide, the water 
must a fortiori be frozen, and would continue so 
long after the temperature rose above the melt- 
ing point of the former substance. We should 
therefore still have snow-fields of snow after the 
melting of those formed of carbonic acid gas, 
either visible as white patches or so covered up 
with dirt as to pass for land. Now there are no 
such additional white patches to be seen, nor, so 
far as we can judge, does any part of the planet 
behave as if it were glacier-bound. 

Second : carbonic dioxide passes, as we saw, 
almost simultaneously into the liquid and solid 
states, especially under slight pressure. Now, 
the pressure is certainly very slight on the 
surface of Mars ; not probably more than, and 
probably less than, one seventh of an atmosphere. 
In consequence, on a rise of temperature the 
frozen carbonic acid gas would there pass prac- 
tically straight from the solid into the gaseous 



THE POLAR CAP 83 

state. Now, from the existence of the surround- 
ing polar sea, we remark that in the substance 
composing the polar caps of Mars this does not 
occur. A considerable portion of it is always 
in the transition state of a liquid. Carbonic di- 
oxide would not thus tarry : water would. 

Third : from the curve of metamorphosis, it is 
evident that the temperature necessary to freeze 
the gas under the pressure of one seventh of an 
atmosphere must lie between — 100° C. and 
—200° C, if not lower. —200° C. is, so far as 
we can judge, about the temperature of inter- 
planetary space, or what would be the tempera- 
ture of the night side of Mars were the planet 
destitute of atmosphere. But there is an atmos- 
phere on Mars, and, even if there were not, on 
melting the carbonic dioxide would itself make 
an atmosphere. This would instantly raise the 
temperature, and under any rise in temperature 
the congealing of the gas at once becomes an 
impossibility. The gas itself thus suggests its 
own refutation. 

There is no such apparent objection to water. 
With an atmosphere properly constituted (and 
there is nothing to show that the Martian at- 
mosphere is not so constituted), the tempera- 
ture might easily rise high enough to melt ice. 
We may therefore conclude water to be the 
most probable solution of the question. 

With such more or less solid ground to 



84 MAES 

stand on, we may now go on to describe the 
behavior of the cap as constituted of snow. 
Whether we call it snow-cap or ice-cap is im- 
material, as, although it would probably be 
deposited as hoar-frost rather than as snow in 
the first instance, owing to the thinness of the 
Martian air, the latter end of either form of the 
substance would be much the same, — glacier- 
ice. 

It will be interesting to examine more in de- 
tail the annual history of the ice-cap, especially 
as this history was unrolled before us last year 
more minutely than has been the case for the 
last fifteen years, and than will be the case for 
fifteen years to come. This was due not only 
to the relative proximity of the planet during 
the last opposition, but to the further fact 
that its south pole was tilted toward us at a 
maximum angle. The vicissitudes which the 
polar cap underwent stood, in consequence, re- 
markably well displayed. To such advantage 
were they seen that it has been possible to con- 
struct a map of the Martian south circumpolar 
regions to a degree of detail such as has never 
been possible before, and which I have accord- 
ingly done. It will be seen from it (on the 
opposite page) how much farther advanced is 
our knowledge of the Martian south pole, and 
the regions about it, than is our knowledge of 
either of our own. It is also pleasing to re- 



Plate II 



igO" '80° 170' 




MAP OF THE SOUTH POLE OF MARS 
Showing the polar cap and its changes in 1894 



Lowell Observatory 
Flagstaff, A. T. 1895 



THE POLAR CAP 85 

member that during this our polar expedition 
we were not frost-bitten for life, nor did we 
have to be rescued by a search party. We lived 
not unlike civilized beings during it all, and we 
actually brought back some of the information 
we went out to acquire. 

On examining the chart in which the succes- 
sive appearances of the southern ice-cap are de- 
picted at different times, from June 3 to October 
13, or, in terms of the Martian time of year, from 
May 1 to July 15, the first point to strike one is 
that the cap was during its whole existence ec- 
centrically placed with regard to the geograph- 
ical pole of the planet. In other words, the pole 
of rotation and the pole of cold did not coincide. 
The latter lay on the average some six degrees 
distant from the former. This shows that the 
isotherms in the southern hemisphere of Mars 
do not coincide with the parallels of latitude. 

The manner of the cap's melting further 
shows that differences of level exist in it. For, 
in addition to melting round its edge, the cap 
proceeded to melt asymmetrically. On the first 
night that Professor W. H. Pickering observed 
it, on May 22, with the six-inch telescope, he 
suspected a rift crossing the cap from longitude 
330° to longitude 170°. This rift grew more 
and more evident, until, in the early part of 
June, it was unmistakable. It grew in visibility 
chiefly from actual growth in size. On June 6 



86 MARS 

it was estimated, on a scale of ruled lines made 
for the purpose, to be about 100 miles wide. 
On June 15 it was similarly found to measure 
350 miles. 

Meanwhile an interesting phenomenon oc- 
curred in the cap on June 7. On that morn- 
ing, at about a quarter of six (or, more precisely, 
on June 8, Ih. 17m., G. M. T.), as I was watch- 
ing the planet, I saw suddenly two points like 
stars flash out in the midst of the polar cap. 
Dazzlingly bright upon the duller white back- 
ground of the snow, these stars shone for a few 
moments and then slowly disappeared. The 
seeing at the time was very good. It is at 
once evident what the other-world apparitions 
were, — not the fabled signal-lights of Martian 
folk, but the glint of ice-slopes flashing for 
a moment earthward as the rotation of the 
planet turned the slope to the proper angle ; 
just as, in sailing by some glass-windowed house 
near set of sun, you shall for a moment or two 
catch a dazzling glint of glory from its panes, 
which then vanishes as it came. But though 
no intelligence lay behind the action of these 
lights, they were none the less startling for 
being Nature's own flash-lights across one hun- 
dred millions of miles of space. It had taken 
them nine minutes to make the journey ; nine 
minutes before they reached Earth they had 
ceased to be on Mars, and, after their travel of 



THE POLAR CAP 87 

one hundred millions of miles, found to note 
them but one watcher, alone on a hill-top with 
the dawn. 

Calculation showed the position of the star- 
points to be in longitude 280° and 290° and 
in latitude 76° south. At this place on the 
planet, then, there was a range of slopes suffi- 
ciently tilted to reflect the Sun from their ice- 
clad sides. On comparing its position with 
Green's map of his observations upon the cap 
at Madeira in 1877, it appeared that this was 
the identical position of the spot where he had 
seen star-points then, and where Mitchell had 
seen them in 1846, to whom they had suggested 
the same conclusion. Green christened them 
the " Mitchell Mountains." At the times both 
these observers saw them, they were detached 
from the rest of the cap. At the time of this 
observation in June, they were still in the midst 
of the cap. We shall see that they eventually 
became islands, just as Green saw them, and 
that the observation in June marked an earlier 
stage in their history. 

On June 10 Mr. Douglass detected a second 
rift in the cap backing the range of slopes. 
And on June 13 I noticed that behind the 
bright points the snow fell off shaded to this 
rift. Meanw^hile a third rift had been made 
out by him, running from longitude 170° to 
longitude 90°, — very nearly, therefore, at right 



88 MARS 

angles to the first rift and debouching into it. 
Bright points continued to be seen at various 
points to the westward round the cap. They 
are marked by crosses on the chart. Through- 
out these daysj the cap was wont to appear 
shaded upon the terminator side, as one might 
expect of a snow or ice slope. During June, 
also, the contour of the cap was apparently 
elliptical. But on June 25 Professor W. H. 
Pickering noted, for the first time, that it no 
longer looked so. The melting had resulted in 
making its asymmetry perceptible. 

On July 1 our Martian polar expedition dis- 
closed what used to be the supreme quest of 
earthly expeditions, — that dream of arctic ex- 
plorers, an open polar sea. On that day Pro- 
fessor Pickering perceived, in the midst of the 
cap, in longitude 260° and latitude 80°, a sheet 
of water about 250 miles long by 150 broad. It 
was in fact the spreading of the first rift about 
midway across the cap, and lay not far from 
the geographical pole of the planet, though not, 
it is to be noticed, near the pole of cold, for it 
lay on the further side of the geographical pole 
from it. There is a touch of the irony of fate 
in this detection of an open polar sea on Mars 
before explorers have succeeded in doing so on 
the Earth. 

In addition to these rifts and other irregu- 
larities of melting, small detached bits of the 



THE POLAR CAP 89 

cap showed from time to time, one being seen 
by Professor Pickering on July 9 in longitude 
284°, and another by him on July 23 in about 
longitude 160°. 

Meanwhile the cap had been steadily decreas- 
ing in size, its progressive diminutions being 
shown on the map in the successive contour 
lines. The polar sea faithfully followed it in 
its shrinkage, even the bays keeping their longi- 
tudes unchanged. But, whereas early in June 
the bay at longitude 270° had been blue, it now 
appeared brown; of that mud-color land does 
from which the water has recently been drained 
off. 

After various vicissitudes, too numerous to 
mention in detail, on August 6 a separate 
patch of snow showed very conspicuous, to the 
left of the main body. The smaller detachment 
lay in longitude 290°, and in latitude 75°-78°. 
Now, on turning to the record of the star-points 
that had appeared two months before, it will be 
seen that this was their position. Here, then, 
was proof of the identity of the star-points seen 
in June with the islands recorded by Mitchell 
and Green. The detached patch was in fact 
the range of slopes left in isolated insularity 
after all about it had melted away. From this 
we have an interesting bit of corroborative testi- 
mony that it stood on higher ground. 

On August 11 the detached patch was yet 



90 MARS 

farther separated from the main body of the 
cap, the smaller patch being many degrees dis- 
tant to the north of either the geographical 
pole or the pole of cold, with water and even 
dry land to the south of it. It will be remem- 
bered, for the points of the compass, that this is 
the southern hemisphere of which we are speak- 
ing, and that, for climatic purposes, north and 
south here stand interchanged. On August 13 
the detached patch is recorded for the last time, 
or, in other words, about this time it melted 
away. The larger one remained, contracting 
in size, however, as time went on. So it con- 
tinued through August, September, and well 
into October. 

On October 12, at lOh. 40m., I made the fol- 
lowing entry about it : " Polar cap has been 
very faint for some time ; barely visible." At 
13h. 26m., or, in other words, at about half 
past one that night, Mr. Douglass measured its 
position and estimated its size, as was his wont 
every few days. He found it to be six degrees 
distant from the planet's pole, in longitude 54°. 
The patch was very small, covering about one 
hundred and fifty miles square. On looking 
at the planet on October 13, at 8h. 15m., to 
his surprise he found the cap gone. Not a 
trace of it could be seen ; nor could either 
he or I detect it during the rest of that night, 
although such was the longitude of the central 



THE POLAR CAP 91 

meridian throughout it as to bring the cap on 
the nearer side of the pole, and therefore show 
it to best advantage. What had certainly been 
there on the 12th was not there on the 13th. 
The ice-cap had disappeared. 

No such occurrence -has ever been chronicled 
before. It is the first time since man began to 
observe the planet that the ice-cap has com- 
pletely disappeared. Hitherto it has been seen 
to diminish to a minimum of from 7° to 4°, and 
then begin to increase again. This last autumn, 
for the first time, it vanished entirely. The 
date of this occurrence was, in Martian chro- 
nology, about July 20. Evidently, for some 
reason unknown to us, it was a phenomenally 
hot season in the southern hemisphere of the 
planet. 

Practically it never reappeared again during 
the season. That it did return occasionally, as 
a very small speck, was from time to time sus- 
pected, and doubtless did take place. Certainly 
it left for some time behind it a glimmer where 
it had been, due presumably to the moisture 
from its melting, still tarrying on the ground 
or lingering in the air. Otherwise, to all intents 
and purposes, where the polar ice-cap and polar 
sea had been was now one ochre stretch of 
desert. 

Having thus followed to its vanishing point 
the polar cap, we will now return to it in the 



92 . MARS 

heyday of its youth, in June, 1894, when it 
was girdled by its broad blue belt. We have 
seen that we have reason to believe this to be 
in all probability a polar sea, a real body of 
water. There is, therefore, water on the sur- 
face of Mars. We also mark that this body of 
water is ephemeral. It exists while the ice- 
cap is melting, and then it somehow vanishes. 
What becomes of it, and whether there be other 
bodies of water on the planet, either permanent 
or temporary, we will now go on to inquire. 

II. AEEOGRAPHY 

As in the course of our inquiry we shall have 
occasion to refer familiarly to different Martian 
features, we had best begin it with some slight 
exposition of Martian geography, or of areo- 
graphy, as it may by analogy be called. To get 
this we will, by the help of Plates III. to XIY., 
suppose ourselves to be viewing the planet 
from some standpoint in space, and watching the 
surface features pass in procession under our 
gaze as the rotation of the planet brings them 
successively round into view. In the matter 
of names the map of the planet toward the end 
of the book, with its accompanying index, will 
give identification. We may thus make a far 
journey without leaving home, and from the 
depths of our arm-chairs travel in spirit to lands 
we have no hope of ever reaching in body. 



AREOGRAPHY 93 

We may add to this the natural delight of the 
explorer, for we shall be gazing upon details of 
Martian geography never till last summer seen 
by man. 

Areography is a true geography, as real as 
our own. Quite unlike the markings upon 
Jupiter or Saturn, where all we see is cloud, 
in the markings on Mars we gaze upon the 
actual surface features of the Martian globe. 
That we do so we know from the permanency 
of the spots and patches thus revealed to us. 
They change in appearance, indeed, according 
to times and seasons, but they alter as true 
surface features would, not like cloud-belts that 
gather to-day and vanish forever to-morrow. 
That the markings are essentially permanent 
has been known ever since Cassini in 1666 
definitely discovered, what Huyghens had 
thought to detect in 1659, the rotation of the 
planet, by means of their periodic presentations. 

The twelve views we shall here scan are of 
the nature of a map, made in November, 1894. 
They represent the ensemble of the drawings 
from this observatory, for about that date. 
The details from these drawings w^ere plotted 
upon a globe, which was then tilted toward the 
observer at the angle at which the Martian 
south pole itself was tilted toward the Earth 
during November, and photographed at inter- 
vals of 30°. The negatives were then made to 



94 MARS 

conform as near as might be to the actual look 
of the planet. To photograph minute planetary 
markings directly is, for reasons too long to 
state here, impossible. The views give between 
them the whole surface of the planet shown us 
at what corresponds to our first of August. 
Thus, neither the polar cap nor the polar sea 
appear in the pictures, for both had then dis- 
appeared. Nor do the southern parts of the so- 
called straits show, for a similar reason. But 
from a knowledge of the features here presented 
the reader will find interpolation of any others 
referred to easy. 

Previous to the present chart, the most de- 
tailed map of the planet was Schiaparelli's, 
made in 1888. On comparison with his, it will 
be seen that the present one substantially con- 
firms all his detail, and adds to it about as much 
more. I have adopted his nomenclature, and 
in the naming of the newly found features 
have selected names conformable to his scheme, 
which commends itself both on practical and on 
poetic grounds. 

We will begin our journey at the origin of 
Martian longitudes and travel west, taking the 
points of the compass as they would appear 
were we standing upon the planet. As all 
astronomical pictures are, for optical reasons, 
upside down, south lies at the top of the pic- 
tures, west to the right, north at the bottom. 



AREOGRAPHY 95 

and east to the left. Mars rotates as the 
Earth does, from west to east, so that day as it 
advances across the face of the planet follows 
the order here shown in Plates III. to XIV., the 
order in which we shall observe them. Places 
on the right of the picture are in the morning 
of their Martian day ; places on the left, in its 
afternoon. To facilitate reference by longitude 
and latitude, the globe has been belted by 
meridians and parallels each 10° apart, and the 
meridians have been numbered along the 
equator. This premised, we will suppose our- 
selves to be standing on the equator at its in- 
tersection with the 0° meridian. (Plate III.) 

It will be noticed that the 0° meridian passes 
through the tip of a triangular peninsula that 
juts out into a dark area curiously forked, half 
way across the picture and about two thirds 
way down it. The tip of this triangle is the 
received Greenwich of Martian longitudes, and 
has been named by Schiaparelli the Fastigium 
Aryn, such having been the name of a mytho- 
logic spot supposed by the ancients to lie mid- 
way between the east and west, the north and 
south, the zenith and nadir. It thus makes a 
fitting name for the starting-point of Martian 
long:itudes and the beo-innino^ of time. The 
dark forked area, called by Proctor " Dawes' 
Forked Bay," is now commonly called the 
Sabaeus Sinus. At the times these marine 



96 MARS 

names were bestowed, it was supposed that the 
dark markings really represented water. We 
have now reason to believe that such is not the 
case. But it is better to keep the old names, 
although I shall employ them in a Pickwickian 
sense, much as we still speak of the Seas of 
the Moon, the Mare Tranquillitatis, or the Mare 
Serenitatis, of which only the adjectives have in 
them anything of truth. 

To the west of the Sabaeus Sinus lies an- 
other dark, wedge-shaped area, longer than 
it but single instead of double. This is the 
Margaritifer Sinus, or the Pearl-bearing Gulf, 
so named before it was known that that name 
possessed any significance. But a prescience 
must have presided over its christening. For 
we now know that there is indeed a pearl at 
the bottom of it, — the round spot shown in 
the picture. 

Two lines will be noticed prolonging the twin 
forks of the Sabaeus Sinus. If we let our look 
follow down them, we shall mark others and 
then yet others, and so we might proceed from 
line to line all over the bright areas of the 
planet. These lines are the famous canals of 
Mars. With regard to their surprising symme- 
try, it is only necessary to say that the better 
they are seen the more symmetrical they look. 
Of the two first mentioned, the right-hand one 
is the Gihon, the left-hand one the Hiddekel, 



Plate III 



^ 


^^^^^_^m' 


f 


1^ 



MARS 
Longitude o° on the Meridian 



Lowell Observatory 
Flagstaff, A. T. 1895 




MARS 
Longitude 30° on the Meridian 



Lowell Observatory 
Flagstaff, A. T. 1895 



AREOGRAPHY 97 

and the spot at the limit of the latter is the 
Lacus Ismenius. From the pearl at the bottom 
of the Margaritifer Sinus, the Oxia Palus, the 
Oxus runs nearly north to the Pallas Lacus, 
while another canal, the Indus, makes off north- 
west. 

Nearly in the centre of the disk are seen two 
of those strange comet-tail peninsulas that con- 
stitute so peculiar a feature of Martian geo- 
graphy. The lower is Deucalionis Regie ; the 
upper, Pyrrhae Regie. Across them show two 
streaks, which, followed up, will be found to 
join other streaks traversing the dark regions. 
These introduce us to Mr. Douglass' discovery 
of a whole system of canals in the dark regions, 
paralleling the system in the bright areas, — 
being similarly straight and similarly inter- 
secting one another, with spots at the intersec- 
tions, making what Mr. Douglass aptly terms a 
checkerboard effect, as we shall see more strik- 
ingly when we get round to the other side of 
the planet. 

In Plate lY. the markings have, under the 
rotation of the planet, all swung 30° to the east, 
thus bringing others into view from the west. 
The great swath obliquely belting the disk is 
the canal called the Jamuna. It was, at the 
time this picture represents it, apparently in 
process of doubling. Crossing it obliquely is 
the Hydraotes. More conspicuous are two dark 



98 MARS 

swaths that make with the Jamuna a nearly 
right-angled triangle. The lower one parallel 
to the edge of the disk is the Dardanus ; the 
other, ending at the south with the Jamuna in 
the Aurorae Sinus, is the Ganges, one of the 
largest and most important of the Martian 
canals. At the date of the drawing, it was dis- 
tinctly double. The doubling is very curiously 
prolonged by a narrow rectangle lying in the 
midst of the dark regions to the south. Some 
idea of the size of these strangely geometrical 
markings may be got by remembering that a 
degree on Mars represents thirty-seven miles. 
Skirting the edge of the dark regions westward, 
we come to a short canal, the Hebe, leading to 
the Fons Juventae, one of the tiniest markings 
perceptible on the disk, from which, however, 
some six canals have been found to radiate. 
Schiaparelli detected it in 1877, searched for 
it in vain in 1879, but at subsequent oppositions 
found it again, happier than Ponce de Leon in 
his futile quest after an earthly Fountain of 
Youth. Proceeding still farther west, we reach 
the entrance to the Agathodaemon, at the point 
where the edge of the dark regions abruptly 
trends southward. This canal brings us to the 
Solis Lacus region, one of the most interesting 
parts of the planet. 

In Plate Y. it has swung round into bet- 
ter view, where we will therefore consider it. 



Plate V 




MARS 
Longitude 6o° on the Meridian 



Lowell Observatory 
Flagstaflf, A. T. 1895 



AREOGRAPHY 99 

The Solis Lacus is a great oval patch, measur- 
ing along its longest diameter five hundred and 
forty miles. With small telescopic power or in 
poor air it appears of uniform tint through- 
out, but under better visual conditions dark 
spots appear in it, and bright causeways, which 
divide it into five portions. Its longitudinal 
dividing line is prolonged into the Nectar, the 
short canal connecting it with the dark regions 
to the east. The Nectar thus appears double. 
Nor does the causeway stop here. It continues 
on between double dark lines until it reaches 
the long rectangular area spoken of before as a 
sort of continuation of the Ganges. 

But a second feature of this region is no less 
noteworthy. Surrounding the Solis Lacus is a 
perfect cordon of canals and spots, the chief of 
which are the Tithonius Lacus, nearly due north, 
and the Lacus Phoenicis, or Phoenix Lake, north- 
west. The spots are strung like beads upon 
the loop of the Agathodaemon and the Dae- 
mon. From the northeast end of this string of 
spots runs the Chrysorrhoas to the Lacus Lunae 
on the fifty-eighth meridian. Below it is the 
Labeatis Lacus, from which the Gigas starts 
west, to be lost in the limb-light. 

In the next plate (Plate YI.), the Solis Lacus 
is central, the Lacus Phoenicis somewhat to the 
right of the centre ; and southwest of the Lacus 
Phoenicis is the Beak of the Sirens, the eastern 



100 MARS 

end of the sea of the same name, which has just 
come round the corner of the disk. The canal 
connecting it with the Phoenix Lake is the 
Araxes ; and at various angles to this, like 
spokes of a wheel about the Phoenix Lake for 
hub, are many more canals, the one lying most 
nearly due south being the Phasis. Connecting 
with this network of canals is a similar network 
of streaks in the dark regions, making a set of 
triangles, from which still other canals run up 
almost straight toward the south pole. 

Between the dark regions and the Beak of 
the Sirens is the peninsula Phaetontis, crossing 
which some way up is a short canal known as 
Herculis Columnae. Due south of the Lacus 
Phoenicis is the spot Ceraunius, joined to the 
Lacus Phoenicis by the Iris, and to the' Titho- 
nius Lacus by the Fortunae. It is also crossed 
by the Gigas, the very long canal in the right- 
hand lower part of the disk, of which we saw 
the beginning in the last plate, and shall not 
see the end till we reach the next one. 

Westward of the Lacus Phoenicis there be- 
gins to show a congeries of spots and connecting 
canals, which come out still more strikingly in 
Plate VII. The great canal beaded with spots, 
which in the picture traverses nearly the centre 
of the disk, is the Eumenides, and its continua- 
tion, the Orcus. Its farther end is lost in the 
limb-light. At an angle to it, running nearly 




MARS 
Longitude 90° on the Meridian 



Lowell Observatory 
Flagstaff, A. T. 1895 



Plate VII 




MARS 
Longitude 120° on the Meridian 



Lowell Observatory 
Flagstaff, A. T. 1895 



AREOGRAPHY 101 

northwest from the Lacus Phoenicis, is the Pyri- 
phlegethon. In this plate the Sea of the Sirens 
is well on, its beak being almost on the central 
meridian. From its north coast strike down 
a great many canals, all going as far as the 
Eumenides and some continuing past it. The 
first one from the Beak of the Sirens is the 
Sirenius. It crosses the Eumenides at the first 
of its large spots after leaving the Phoenix Lake, 
the Lucus Arsine. To the next spot, known 
as the Nodus Gordii, the Gorgon comes down 
from the centre of the coast-line, meeting the 
Gigas, which itself debouches, at the west end 
of the sea, into what is called the Sinus Titanum, 
or Gulf of the Titans. 

In Plate YIII. the Sinus Titanum has come 
round into view. Owing to its conspicuousness 
at certain seasons, it is one of the most impor- 
tant features on the planet to us, and seems to 
be to the planet itself, as some seven canals 
radiate from it. These are the Gigas, previ- 
ously described, and to the right, in the order 
here enumerated, the Steropes, the Brontes, the 
Titan, — the one straight down the disk, — the 
Arges, the Gyes, and the Tartarus; the last 
traveling to the Trivium Charon tis invisible 
in this plate. Of the separate existence of the 
Arges and the Gyes I am not quite certain. 
These great canals show like the sticks of a fan, 
with the Sinus itself for pivot. 



102 MARS 

The Sea of the Sirens is now nearly central. 
To the west, dividing it from the Mare Cimme- 
rium^ which is just coming into view, is the 
peninsula Atlantis, curiously uniting the conti- 
nents to the islands to the south. Belting the 
disk from east to west is the Eumenides-Orcus, 
strung with spots. 

Parallel to the Eumenides-Orcus, and skirt- 
ing the north shore of the Sea of the Sirens, is 
the Erynnis. Half way between this and the 
Eumenides is another parallel canal, the Parcae. 
Curving round the bottom of the disk is a chain 
of canals, the Pyriphlegethon, Acheron, and 
Erebus, the last of which runs to the Trivium 
Charontis. At the junctions of these various 
canals may be seen any number of spots. 

On the next plate (Plate IX.) the Trivium 
Charontis itself has come into view toward the 
lower right-hand part of the disk. Two nearly 
parallel canals, a double Hades, join it to the Pro- 
pontis, the spot almost at the limb. The Titan 
shows well near the centre of the disk. Were 
the centre ten degrees farther east, the canal 
would appear more striking yet. For so straight 
is it, and so nearly due north and south does it 
lie, that when it comes to the meridian it seems 
that meridian itself. On this plate we have the 
western end of the Eumenides-Orcus, at whose 
eastern end we began several plates back when 
we left the Phoenix Lake. This will give some 



Plate VIII 




MARS 
Longitude 150° on the Meridian 



Lowell Observatory 
Flagstaff, A. T. 1895 



Plate IX 




MARS 
Longitude i8o° on the Meridian 



Lowell Observatory 
Flagstaff, A. T. 1895 



AREOGRAPHY 103 

idea of the immense length of the canal, which 
is no less than three thousand four hundred and 
fifty miles long. Nearly in the centre of the 
disk is the peninsula Atlantis, the most easterly 
of the set of comet- tail peninsulas similar to 
those seen in Plate I., all connecting the so- 
called continent with the islands to the south. 
These islands look not unlike great vertebrae 
of the planet's backbone, in consequence of the 
canals which cut them up so symmetrically. 
Atlantis shows well, between Mare Sirenum and 
Mare Cimmerium, two areas suggestively alike 
in general shape and directional trend. Both 
are seen to be crossed by canals which connect, 
at what resemble nicks in the coast-line, with 
the canals in the bright regions. 

In Plate X. the Mare Cimmerium is cen- 
tral. So, also, well down the disk, is the Tri- 
vium Charontis. This is a very important 
junction, no less than nine canals already being 
known to connect with it, which, taken in the 
order, east, north, west, and south, are the 
Orcus, the Erebus, the twin Hades, the Styx, 
the Cambyses, the Cerberus, the Laestrygon, 
the Tartarus, and so back to the Orcus again. 
In this picture the Laestrygon traverses nearly 
the centre of the disk. To the right of the 
Trivium Charontis is the region called Elysium, 
one of the brightest parts of the planet. It 
was here that Mr. Douglass made his interest- 



104 MARS 

ing observation^ last Septemberj of a remarkable 
change of tint from bright to sombre, and back 
to bright again, in the course of forty-eight 
hours ; suggesting perhaps the formation and 
dissipation of cloud, perhaps the deposition and 
subsequent melting of hoar-frost over an area 
of some hundreds of square miles. 

Eeturning to the Mare Cimmerium, we ob- 
serve in the middle of it a long, lighter streak, 
Cimmeria, scarcely perceptible at this last oppo- 
sition, and, barring its western end, the second 
in the procession of similarly inclined peninsulas 
that follow one another westward upon this side 
of the planet, the peninsula Hesperia, a place 
with a history, as will appear later on. 

In the next picture (Plate. XI) Hesperia is 
central, dividing the Mare Cimmerium on the 
left from the Mare Tyrrhenum on the right. 
The lower end of the latter is called the Syrtis 
Minor, in contradistinction to the Syrtis Major, 
which is just appearing round the western limb. 
From the bay, so to speak, upon the left of 
Hesperia, two canals proceed down the disk in 
divergent directions, — the most easterly one 
the Aethiops, the other the Achelous. From 
the Syrtis Minor proceed two others, more or 
less similarly inclined, — the Lethes and the 
Amenthes. 

To the west of Hesperia and parallel to it is 
a third comet-tail peninsula, Lemuria, connect- 




MARS 
Longitude 210° on the Meridian 



Lowell Observatory 
Flagstaff, A. T. 1895 




MARS 
Longitude 240° on the Meridian 



Lowell Observatory 
Flagstaff, A. T. 1895 



Plate XII 




MARS 
Longitude 270° on the Meridian 



Lowell Observatory 
Flagstaff, A, T. 1895 



AREOGRAPHY 105 

ing Ausonia at the south with Libya to the 
north, Libya being upon the equator. This 
region (Plate XII.) is interesting as having been 
the scene of great changes at previous oppo- 
sitions. There used to be a spot, the Lake 
Moeris, in the midst of it, joined by the Nepen- 
thes — the canal running east and west about 
eight degrees north of the equator — to the 
Syrtis Major, the great dark gulf somewhat to 
the west of the central meridian in the picture. 
Latterly the Syrtis Major seems to have en- 
croached upon Libya, and, at the last opposi- 
tion, only the faintest glimpses could be got of 
Lake Moeris, which showed chiefly as a bay of 
the Syrtis Major itself. Here, as elsewhere, I 
use aquatic names with terrestrial understand- 
ing. 

Parallel in a general way to the Nepenthes, 
and about as much below it as it is below the 
coast-line, lies the Astapus, which joins the bot- 
tom of the Syrtis Major to the ends of the 
Amenthes, Lethes, and Achelous. 

In Plate XIII. two features are striking, both 
not far from central on the disk, — the lower, 
the Syrtis Major ; the upper, Hellas. The 
Syrtis Major was the first marking to be cer- 
tainly recognized on Mars. It appears in a 
drawing by Huyghens made on October 13, 
1659, the first drawing of Mars worthy the 
name ever made by man, and reproduced on 



106 MARS 

page 20 from Flammarion's ^' La Planete Mars/* 
It is thus our oldest Martian acquaintance. 
Hellas is the surprisingly round, bright area 
nearly on the meridian, and nearly half way 
from the equator to the south pole. It is very 
strangely quartered by two canals, the Alpheus, 
dividing it almost due north and south; and the 
Peneus, cutting it almost due east and west. 
Between it and the Syrtis Major is the Mare 
Hadriaticum, a blue-green area intersected by 
bright causeways and seamed by dark canals. 

In the lower right-hand portion of the disk is 
an important region, bounded on the east by 
the Syrtis Major, on the north by the Nilosyrtis 
and the Protonilus, on the west by the Hidde- 
kel, and on the south by the long dark area 
to the north of Deucalionis Regio. Its south- 
eastern cape is the Hammonis Cornu ; its south- 
western one, which appears in Plate XIY., is 
the Edom promontory. It is a region prolific 
in double canals. The two - most important of 
these are the Phison and the Euphrates. Both 
start from the centre of the coast of the long 
dark area between the Deucalionis Regio and 
the continent, and run, the Phison northeast to 
the western end of the Nilosyrtis, in longitude 
300°, latitude 33° south ; the Euphrates, nearly 
due south to the Lacus Ismenius, longitude 
337°, latitude 37° south, where it connects with 
the Hiddekel. Parallel to the coast-line and 



Plate XIII 




MARS 
Longitude 300° on the Meridian 



Lowell Observatory 
Flagstaff, A. T. 1895 



Plate XIV 




MARS 
Longitude 330° on the Meridian 



Lowell Observatory 
Flagsta£f, A. T. 1895 



SEAS 107 

about 15° to the north of it is, on the east, the 
Typhon, shown double ; on the west the Orontes, 
still single. Two other doubles shown in the 
picture I saw also in this region, though I am 
not yet certain that they are distinct from the 
Phison and the Euphrates, as the four were not 
seen together. I have introduced them in the 
place where I saw them, because, first, no op- 
tical effect explains any such shift ; and, second, 
they run through and to well-seen spots, which 
renders it more likely that they are distinct 
canals. 

Between the Euphrates and the Sabaeus 
Sinus are several canals and spots that show 
the minute manner in which the Martian sur- 
face is cut up. But so much only hints at the 
state of things existent there. From the mark- 
ings, not well enough seen to admit of mapping, 
it is apparent that the system of lines and spots 
is very complete all over the planet. 

This brings us back again to the Sabaeus 
Sinus and the Fastigium Aryn, from which we 
set out, after a journey which it takes the ro- 
tation of the planet twenty-four hours' thirty- 
seven minutes and about twenty- three seconds 
to accomplish. 

III. SEAS. 

While it existed in any size, the polar sea 
was bordered on the north, all the way round 



108 MARS 

and during all the time it was visible, by blue- 
green areas. These blue-green areas were 
strewn with several more or less bright regions, 
while below them came the great reddish-ochre 
stretches of the disk. Now, the blue-green 
areas have generally been considered to be seas, 
just as the reddish-ochre regions have been 
held to be land. That the latter are land there 
is very little doubt ; not only land, but nothing 
but land, — land very pure and simple ; that is, 
deserts. For they behave just as deserts should 
behave, that is, by not behaving at all; re- 
maining, except for certain phenomena to be 
specified later, unchangeable. 

With the so-called seas, however, the case is 
different. Several important facts conspire to 
throw grave doubt, and worse, upon their 
aquatic character. To begin with, they are of 
every grade of tint, — a very curious feature 
for seas to exhibit, unless they were every- 
where but a few feet deep ; which again is a 
most singular characteristic for seas that cover 
hundreds of thousands of square miles in ex- 
tent, — seas, that is, as big as the Bay of Ben- 
gal. The Martian surface would have to be 
amazingly flat for this to be possible. We 
know it to be relatively flat, but to be as flat as 
all this would seem to pass the bounds of credi- 
ble simplicity. Here also Professor W. H. Pick- 
ering's polariscope investigations come in with 



SEAS 109 

effect, for he found the Hght from the supposed 
seas to show no trace of polarization. Hence 
these were probably not water. 

In parenthesis we may here take notice of 
the absence of a certain phenomenon whose 
presence, apparently, should follow upon water 
surfaces such as the so-called seas would offer 
us. Although its absence is not perhaps defini- 
tive as to their marine character, it is certainly 
curious, and worth noting. If a planet were 
covered by a sheet of water, that water surface 
would, mirror-like, reflect the sun in one more 
or less definite spot. Looked at from a dis- 
tance, this spot would, were it bright enough^ 
be seen as a high light on the dark background 
of the ocean about it. It would seem to be a 
fixed star at a certain point on the disk, the 
surface features rotating under it. The neces- 
sary position is easily calculated, and this shows 
that parts of the so-called seas, especially at 
oppositions like the last one, pass imder the 
point. There remains merely the question of 
sufficient brilliancy in the spot for visibility; 
but as in the case of Mars its brilliancy should 
be equal to that of a star of the third magni- 
tude, it would seem brilliant enough to be seen. 
No such starlike effect in such position has ever 
been noticed coming from the blue-green re- 
gions. From this bit of negative evidence, to 
be taken for what it is worth, we return again 
to what there is of a positive sort. 



110 MARS 

Not only do different parts of the so-called 
seas contrast in tint with one another, but the 
same part of the same sea varies in tint at dif- 
ferent times. Schiaparelli noticed that, at suc- 
cessive oppositions, the same sea showed differ- 
ent degrees of darkness, and he suggested that 
the change in tone was dependent in some way 
upon the Martian seasons. 

Observations at Flagstaff have demonstrated 
this to be the case, for it has been possible to 
see the tints occur consecutively. In conse- 
quence, we know not only that changes take 
place on the surface of Mars other than in the 
polar cap, and very conspicuous ones too, but 
that these are due to the changing seasons of 
the planet's year. We will now see what they 
look like. 

To the transubstantiation of changes of the 
sort it is a prime essential that the drawings 
from whose comparison the contrast appears 
should all have been made by the same person, 
at the same telescope, under as nearly as possi- 
ble the same atmospheric conditions, since other- 
wise the personal equation of the observer, the 
impersonal inequalities of instruments, and the 
special atmosphere of the station play so large 
a part in the result as to mask that other factor 
in the case, any change in the planet itself. 
How easily this masking is accomplished ap- 
pears from drawings made by different ob- 



Plate XV 




Fig. I. Syrtis Major at June presentation 
Long. 290°. Lat. centre of disk. 24° South 




Fig. IL Syrtis Major ai (Jciooer presentation 
Long. 305°. Lat. centre of disk 20° South 

SYRTIS MAJOR 
Showing seasonal change during 1894 



Lowell Observatory 
Flagstaff, A. T. 1894 



SEAS 111 

servers of tlie same Martian features at substan- 
tially the same moment. Several interesting 
specimens of such personal peculiarities may be 
seen by the curious in Flammarion's admirable 
thesaurus, '^ La Planete Mars." In some of these 
likenesses of the planet it is pretty certain that 
Mars would never recognize himself. 

To have drawings simply swear at one an- 
other across a page is, in the interests of de- 
duction, objectionable. For their testimony to 
be worth having, they must agree to differ. 
If, therefore. Mars is to be many, his draughts- 
man must be one. So much, at least, is fulfilled 
by the drawings in which the changes now to be 
described are recorded ; for they w^ere all made 
by me, at the same instrument, under the same 
general atmospheric conditions. As the same 
personality enters all of them, it stands, as be- 
tween them, eliminated from all, to increased 
certainty of deduction. Since, furthermore, 
the drawings were all made in the months 
preceding and following one opposition, change 
due to secular variation is reduced to a mini- 
mum. As a matter of fact, the changes are 
such as to betray their own seasonal character. 
They constitute a kinematical as opposed to a 
statical study of the planet's surface. 

The changes are much more evident than 
might be supposed. Indeed, they are quite un- 
mistakable. As for their importance, it need 



112 MARS 

only be said that deduction from them furnishes, 
in the first place, inference that Mars is a living 
world, subject to an annual cycle of surface 
growth, activity, and decay ; and shows, in the 
second place, that this Martian yearly round of 
life must differ in certain interesting particulars 
from that which forms our terrestrial expe- 
rience. The phenomena evidently make part 
of a definite chain of changes of annual devel- 
opment. So consecutive, and, in their broad 
characteristics, apparently so regular, are these 
changes, that I have been able to find corrobora- 
tion of what appears to be their general scheme 
in drawings made at a previous opposition. In 
consequence, I believe it will be possible in future 
to foretell, with something approaching the cer- 
tainty of our esteemed weather bureau's prog- 
nostications, not indeed what the weather will 
be on Mars, — for, as we have seen, it is more 
than doubtful whether Mars has what we call 
weather to prognosticate, — but the aspect of 
any part of the planet at any given time. 

The changes in appearance now to be chroni- 
cled refer, not to the melting of the polar 
snows, except as such melting forms the neces- 
sary preliminary to what follows, but to the 
subsequent changes in look of the surface itself. 
To their exposition, however, the polar phe- 
nomena become inseparable adjuncts, since they 
are inevitable ancillaries to the result. 



SEAS 113 

With the familiar melting of the snow-cap 
begins the yearly round of the planet's life. 
With the melting of our own arctic or antarctic 
cap might similarly be said to begin the earth's 
annual activity. But here at the very outset 
there appears to be one important difference be- 
tween the two planets. On the earth the rela- 
tion of the melting of the polar snows to the 
awakening of surface activity is a case oipost 
hoc simply ; on Mars it seems to be a case of 
propter hoc as well. For, unlike the earth, 
which has water to spare, and to which, there- 
fore, the unlocking of its polar snows is a matter 
of no direct economic value. Mars is apparently 
in straits for the article, and has to draw on its 
polar reservoir for its annual supply. Upon 
the melting of its polar cap, and the transfer- 
ence of the water thus annually set free to go 
its rounds, seem to depend all the seasonal phe- 
nomena on the surface of the planet. 

The observations upon which this deduction 
is based extend over a period of nearly six 
months, from the last day of May to the 22d of 
November. They cover the regions from the 
south pole to about latitude forty north. That 
changes analogous to those recorded, differing, 
however, in details, occur six Martian months 
later in the planet's northern hemisphere, is 
proved by what Schiaparelli has seen ; for 
though the general system is, curiously, one for 



114 MARS 

the whole planet, the particular character of 
different parts of the surface alters the action 
there to some extent. 

For an appreciation of the meaning of the 
changes, it is to be borne in mind through- 
out that the vernal equinox of Mars' southern 
hemisphere occurred on April 7, 1894; the 
summer solstice of the same hemisphere on 
August 31 ; and its autumnal equinox on Feb- 
ruary 7, 1895. 

On the 31st of May, therefore, it was toward 
the end of April on Mars. The south polar cap 
was, as we have seen, very large, and the polar 
sea in proportion. That the polar sea was the 
darkest and the bluest marking on the disk im- 
plies that it was, at least, the deepest body of 
water on the planet, whether the so-called seas 
were seas or not. But from the fact that it was 
quite wide, — 350 miles, — and that it all event- 
ually vanished, it can hardly have been very 
deep. Its relative appearance, therefore, casts 
a first doubt upon the fact that the others were 
seas at all. This polar sea plays deus ex ma- 
china to all that follows. 

So soon as the melting of the snow was well 
under way, long straits, of deeper tint than 
their surroundings, made their appearance in 
the midst of the dark areas. I did not see them 
come, but as I afterward saw them go it is 
evident that they must have come. They were 



SEAS 115 

already there on tlie last day of May. The 
most conspicuous of them lay between Noachis 
and Hellas, in the Mare Australe. It began in 
the great polar bay, and thence traversed the 
Mare Erythraeum to the Hourglass Sea (Syr- 
tis Major). The next most conspicuous one 
started in the other bay, and came down be- 
tween Hellas and Ausonia. Although these 
straits were distinguishably darker than the 
seas through which they passed, the seas them- 
selves were then at their darkest. The fact 
that these straits traversed the seas suffices to 
raise a second doubt as to the genuineness of 
seas ; the first suspicion as to their character — 
coming from their being a little oif color ; not so 
blue, that is, as what we practically know to be 
water, the polar sea — finding thus corrobora- 
tion. It will appear later that in all probability 
the straits themselves were impostors, and that 
neither seas nor straits were water. 

The appearance of things at this initial stage 
of the Martian Nile-like inundation last June 
was most destructive to modern maps of Mars, 
for all the markings between the south polar 
cap and the continental coast-line seemed with 
one consent to have, as nearly as might be, ob- 
literated themselves. 

It was impossible to fix any definite boun- 
daries to the south temperate chain of islands, 
so indistinguishably did the light areas and the 



116 MAES 

dark ones merge into each other. What was 
still more striking, the curious peninsulas which 
connect the continent with the chain of islands 
to the south of it, and form so singular a fea- 
ture of the planet's geography, were invisible. 
One continuous belt of blue-green stretched 
from the Syrtis Major to the Columns of Her- 
cules. 

For some time the dark areas continued 
largely unchanged in appearance ; that is, dur- 
ing the earlier and most extensive melting of 
the snow-cap. After this their history became 
one long chronicle of fading out. Their lighter 
parts grew lighter, and their darker ones less 
dark. For, to start with, they were made up 
of many tints ; various shades of blue-green 
interspersed with glints of orange-yellow. The 
gulfs and bays bordering the continental coast 
were the darkest of these markings; the long 
straits between the polar sea and the Syrtis 
Major were the next deepest in tone. 

The first marked sign of change was the re- 
appearance of Hesperia. Whereas in June it 
had been practically non-existent, by" August it 
had become perfectly visible and in the place 
where it is usually depicted. In connection 
with its reappearance two points are to be 
noted : first, the amount of the change, for 
Hesperia is a stretch of land over two hundred 
miles broad by six hundred miles long; and. 



Plate XVI 




Fig. I. Hesperia at June presentation 
Long. 242°. Lat. centre of disk 24° South 




Fig. n. Hesperia at August presentation 
Long. 247°. Lat. centre of disk 17° South 



Fig. in. Hesperia at October presentation 
Long. 237°. Lat. centre of disk 21° South 



HESPERIA 
Showing seasonal change during 1894 



Lowell Observatory 
Flagstaff, A. T. 1894 



SEAS 117 

secondly, the fact that its previous invisibility 
was not due to any sort of obscuration. The 
persistent clear-cut character of the neighbor- 
ing coast-line during the whole transformation 
showed that nothing of the nature of mist or 
cloud had at any time hidden the peninsula 
from view. A something was actually there 
in August which had not been there in June. 

As yet nothing could be seen of Atlantis. It 
was not until the 30th of October that I caught 
sight of it. About the same time, the straits 
between the islands, Xanthus, Scamander, Psy- 
chrus, and Simois, came out saliently dark, 
a darkness due to contrast. The line of south 
temperate islands, with their separate identity, 
was then for the first time apparent. 

Meanwhile the history of Hesperia continued 
to be instructive. From having been absent in 
June and conspicuous in August, it returned in 
October to a mid-position of visibility. Vacil- 
lating as these fluctuations in appearance may 
seem at first sight, they were really quite con- 
sistent \ for they were probably due to progres- 
sive change in the one direction, a change that 
was manifested first in Hesperia itself, and then 
in the regions round about it. From June 
to August, Hesperia changed from a previous 
blue-green, indistinguishable from its surround- 
ings, to yellow, the parts adjacent remaining 
much as before. As a consequence, the pe- 



118 MARS 

ninsula stood out in marked contrast to the 
still deep blue-green regions by its side. Later 
the surroundings themselves faded, and their 
bleaching had the effect of once more partially 
obliterating Hesperia. 

While Hesperia was thus getting itself no- 
ticed, the rest of the south temperate zone, as 
we may call it for identification's sake, was un- 
obtrusively pursuing the same course. Whereas 
in June all that part of the disk comprising the 
two Thyle, Argyre II., and like latitudes was 
chiefly blue-green, by October it had become 
chiefly yellow. Still further south, what had 
been first white, then blue, then brown, turned 
ochre. 

Certain smaller details of the change that 
came over the face of the dark regions at the 
time were as curious as they were marked. For 
example, the Fastigium Aryn, the tip of the tri- 
angular cape which, by jutting out from the 
continent, forms the forked bay called the Sa- 
baeus Sinus, and which, because of its easy 
identification, has been selected for the zero 
meridian of Martian longitudes, began in Oc- 
tober to undergo strange metamorphosis. On 
October 15 it shot out a sort of tail southward. 
On the 16th this tail could be followed all the 
way to Deucalionis Eegio, to which it made a 
bridge across from the continent, thus cutting 
the Sabaeus Sinus completely in two. After it 



SEAS 119 

had thus appeared, it continued visible up to 
the close of the observations sufficiently detailed 
to show it. 

Another curious causeway of the same sort 
made its appearance in November, connecting 
the promontory known as Hammonis Cornu 
with Hellas. Both of these necks of orange- 
ochre were of more or less uniform breadth 
throughout. 

The long, dark streaks that in June had 
joined the Syrtis Major to the polar sea had 
by October nearly disappeared ; in their south- 
ern parts they had vanished completely, and 
they had very much faded in their northern 
ones. The same process of fading uncovered 
certain curious rhomboidal bright areas in the 
midst of the Syrtis Major. 

It will be seen that the extent of these 
changes was enormous. Their size, indeed, was 
only second in importance to their character; 
for it will also have been noticed that the 
changes were all in one direction. A whole- 
sale transformation of the blue-green regions 
into orange-ochre ones was in progress upon 
that other world. 

What can explain so general and so consecu- 
tive a change in hue ? Water suggests itself ; 
for a vast transference of water from the pole 
to the equator might account for it. But there 
are facts connected with the change which seem 



120 MARS 

irreconcilable with the idea of water. In the first 
place, Professor W. H. Pickering found that the 
light from the great blue-green areas showed no 
trace of polarization. This tended to strengthen 
a theory put forth by him some years ago, that 
the greater part of the blue-green areas are not 
water, but something which at such a distance 
would also look blue-green, namely, vegetation. 
Observations at Flagstaff not only confirm this, 
but limit the water areas still further ; in fact, 
practically do away with them entirely. Not 
only do the above polariscopic tests tend to this 
conclusion, but so does the following observa- 
tion of mine in October. 

Toward the end of October, a strange, and, 
for observational purposes, a distressing phe- 
nomenon took place. What remained of the 
more southern dark regions showed a desire to 
vanish, so completely did those regions proceed 
to fade in tint throughout. This was first no- 
ticeable in the Cimmerian Sea, then in the Sea 
of the Sirens, and in November in the Mare 
Erythraeum about the Lake of the Sun. The 
fading steadily progressed until it had advanced 
so far that in poor seeing the markings were 
almost imperceptible, and the planet presented 
a nearly uniform ochre disk. 

This was not a case of obscuration ; for in 
the first place it was general, and in the second 
place the coast-lines were not obliterated. The 



SEAS 121 

change, therefore, was not due to clouds or 
mist. 

What was suggestive about the occurrence 
was that it was unaccompanied by a correspond- 
ing increase of blue-green elsewhere. It was 
not simply that portions of the planet's surface 
changed tint, but that, taking the disk in its 
entirety, the whole amount of the blue-green 
upon it had diminished, and that of the orange- 
yellow had proportionally increased. Mars 
looked more Martian than he had in June. 
The canals, indeed, began at the same time to 
darken ; but, highly important as this was for 
other reasons, the whole area of their fine lines 
and associated patches did not begin to make 
up for what the dark regions lost. 

If the blue-green color was due to water, 
where had all the water gone ? Nowhere on 
the visible parts of the planet ; that is certain. 
Nor could it very well have gone to those north 
circumpolar regions hid from view by the tilt 
of the disk ; for there was no sign of a growing 
north polar cap, and, furthermore, Schiaparelli's 
observations upon that cap show that there 
should not have been. At the opposition of 
1881, he found that it developed late, appar- 
ently one month or so after the vernal equinox 
of its hemisphere, whereas at the time the above 
change occurred it was not long after that hemi- 
sphere's winter solstice. 



122 MARS 

But ifj instead of being due to water, the 
blue-green tint had been due to leaves and 
grasses, just such a fading out as was observed 
should have taken place as autumn came on, 
and that without proportionate increase of green 
elsewhere ; for the great continental areas, be- 
ing desert, are incapable of supporting vegeta- 
tion, and therefore of turning green. 

Thus we see that several independent phe- 
nomena all agree to show that the blue-green 
regions of Mars are not water, but, generally 
at least, areas of vegetation ; from which it fol- 
lows that Mars is very badly off for water, and 
that the planet is dependent on the melting of 
its polar snows for practically its whole supply. 

Such scarcity of water on Mars is just what 
theory would lead us to expect. Mars is a 
smaller planet than the Earth, and therefore is 
relatively more advanced in his evolutionary 
career. He is older in age, if not in years ; for 
whether his birth as a separate world antedated 
ours or not, his smaller size, by causing him to 
cool more quickly, would necessarily age him 
faster. But as a planet grows old, its oceans, 
in all probability, dry up, the water retreating 
through cracks and caverns into its interior. 
Water thus disappears from its surface, to say 
nothing of what is being continually imprisoned 
by chemical combination. Signs of having thus 
parted with its oceans we see in the case of the 



Plate XVII 




Fig. I. Sea of the Sirens at June presentation 
Long. 141°. Lat. centre of disk 24° South 

Fig. II. Sea of the Sirens at November presentation 
Long. 156°. Lat. centre of disk 22° South 

SEA OF THE SIRENS AND ATLANTIS 

AT THE OPPOSITION OF 1894 

Showing seasonal change 



Lowell Observatory 
Flagstaff, A. T. 1894 



SEAS 123 

Moon, whose so-called seas were probably seas 
in their day, but have now become old sea- 
bottoms. On Mars the same process is going 
on, but would seem not yet to have progressed 
so far, the seas there being midway in their 
career from real seas to arid depressed deserts ; 
no longer water surfaces, they are still the low- 
est portions of the planet, and therefore stand 
to receive what scant water may yet travel 
over the surface. They thus become fertihzed, 
while higher regions escape the freshet, and 
remain permanently barren. That they were 
once seas we have something more than gen- 
eral inference to warrant us in believinsf. 

There is a certain peculiarity about the sur- 
face markings of Mars, which is pretty sure to 
strike any thoughtful observer who examines 
the planet's disk, with a two- or a three-inch 
object-glass, — their singular sameness night 
after night. With quite disheartening regu- 
larity, each evening presents him with the same 
appearance he noted the evening before, — a 
dark band obliquely belting the disk, strangely 
keeping its place in spite of the nightly pro- 
cession of the meridians ten degrees to the east, 
in consequence of our faster rotation gaining 
on the slower rotation of Mars. By attention, 
he will notice, however, that the belt creeps 
slowly upwards towards the pole. Then sud- 
denly some night he finds that it has slipped 



124 MARS 

bodily down, to begin again its Sisyphus-like, 
inconclusive spiral climb. 

Often as this rhumb line must have been no- 
ticed, no explanation of it has ever, to my 
knowledge, been given. Yet so singular an ar- 
rangement points to something other than 
chance. Suspicion of its non-fortuitous charac- 
ter is strengthened when it is scanned through 
a bigger glass. Increase of aperture discloses 
details that help explain its significance. With 
sufficient telescopic power, the continuity of the 
dark belt is seen to be broken by a series of 
parallel peninsulas or semi-peninsulas that jut 
out from the lower edge of the belt, all running 
with one accord in a southeasterly direction, 
and dividing the belt into a similar series of 
parallel dark areas. Such oblong areas are the 
Mare Tyrrhenum, the Mare Cimmerium, the 
Mare Sirenum, and those unnamed straits that 
stretch southeasterly from the Aurorae Sinus, 
the Margaritifer Sinus, and the Sabaeus Sinus. 
The islands and peninsulas trending in the same 
direction are Ausonia, Hesperia, Cimmeria, 
Atlantis, Pyrrhae Kegio, Deucalionis Regio, and 
the two causeways from the Fastigium Aryn 
and Hammonis Cornu. It will further be no- 
ticed that these areas lie more nearly north 
and south as they lie nearer the pole, and 
curve in general to the west as they approach 
the equator. 



SEAS 125 

With this fact noted, let us return to the 
water formed by the melting of the ice-cap, at 
the time it is produced around the south pole. 
We may be sure it would not stay there long. 
No sooner liberated from its winter fetters than 
it would begin, under the pull of gravity, to 
run toward the equator. The reason why it 
would flow away from the pole is that it would 
find itself in unstable equilibrium where it was. 
Successive depositions of frost would have piled 
up a mound of ice which, so long as it remained 
solid, cohesion would keep in that unnatural 
position ; but the moment it changed to a liquid 
this would flow out on all sides, seeking its 
level. Once started, its own withdrawal would 
cause the centre of gravity to shift away from 
the pole, and this would pull the particles of 
the water yet more toward the equator. Each 
particle would start due north ; but its course 
would not continue in that direction, for at each 
mile it traveled it would find itself in a lower 
latitude, where, owing to the rotation of the 
planet, the surface would be whirling faster to- 
ward the east, inasmuch as a point on the equa- 
tor has to get over much more space in twenty- 
four hours than one nearer the pole. In short, 
supposing there were no friction, the surface 
would be constantly slipping away from under 
the particle toward the east. As a result, the 
northerly motion of the particle would be con- 



126 MAES 

tinually clianging with regard to the surface into 
a more and more westerly one. If the surface 
were not frictionless, friction would somewhat 
reduce the westerly component, but could never 
wholly destroy it without stopping the particle. 

We see, therefore, that any body, whether 
solid, liquid, or gaseous, must, in traveling away 
from the pole of a sphere or spheroid, neces- 
sarily deviate to the west as it goes on, if the 
spheroid itself revolve, as Mars does, in the op- 
posite direction. 

Now this inevitable trend induced in any- 
thing flowing from the pole to the equator is 
precisely the one that we notice stereotyped so 
conspicuously in the Martian south temperate 
markings. Here, then, we have at once a 
suspiciously suggestive hint that they once held 
water, and that that water flowed. 

Corroborating this deduction is the fact that 
the northern sides of all the dark areas are very 
perceptibly darker than the southern ones ; for 
the northern side is the one which a descending 
current would plough out, since it is the north- 
ern coasts that would be constantly opposing 
the current's northerly inertia. Consequently, 
although at present the descending stream be 
quite inadequate to such task, it still finds its 
way, from preference, to these lowest levels, 
and makes them greener than the rest. 

Though seas no longer, we perceive, then, 



SEAS 127 

that there is some reason to believe the so-called 
seas of Mars to have been seas in their day, and 
to be at the present moment midway in evo- 
lution from the seas of Earth to the seas of the 
Moon. 

Now, if a planet were at any stage of its 
career able to support life, it is probable 
that a diminishing water supply would be the 
beginning of the end of that life, for the air 
would outlast the available water. Those of 
its inhabitants who had succeeded in surviving 
would find themselves at last face to face with 
the relentlessness of a scarcity of water con- 
stantly growing greater, till at last they would 
all die of thirst, either directly or indirectly ; 
for either they themselves would not have 
water enough to drink, or the plants or animals 
which constituted their diet would perish for 
lack of it, — an alternative of small choice to 
them, unless they were conventionally particular 
as to their mode of death. Before this lament- 
able conclusion was reached, however, there 
would come a time in the course of the planet's 
history when water was not yet wanting, but 
simply scarce and requiring to be husbanded ; 
when, for the inhabitants, the one supreme 
problem of existence would be the water prob- 
lem, — how to get water enough to sustain life, 
and how best to utilize every drop of water 
they could get. 



128 MAES 

Mars is, apparently, in this distressing plight 
at the present moment, the signs being that its 
water supply is now exceedingly low. If, 
therefore, the planet possess inhabitants, there 
is but one course open to them in order to sup- 
port life. Irrigation, and upon as vast a scale 
as possible, must be the all-engrossing Martian 
pursuit. So much is directly deducible from 
what we have learned at Flagstaff of the phy- 
sical condition of the planet, quite apart from 
any question as to possible inhabitants. What 
the physical phenomena assert is this : if there 
be inhabitants, then irrigation must be the chief 
material concern of their lives. 

At this point in our inquiry, when direct de- 
duction from the general physical phenomena 
observable on the planet's surface shows that, 
were there inhabitants there, a system of irriga- 
tion would be an all-essential of their existence, 
the telescope presents us with perhaps the most 
startling discovery of modern times, — the so- 
called canals of Mars. These strange pheno- 
mena, together with the inferences to be drawn 
from them, we will now proceed to envisage. 



IV 

CANALS 
I. FIEST APPEARANCES 

In the last chapter we saw how badly off for 
water Mars, to all appearance, is ; so badly off 
that inhabitants of that other world would have 
to irrigate to live. As to the actual presence 
there of such folk, the broad physical character- 
istics of the planet express no opinion beyond 
the silence of consent, but they have some- 
thing very vital to say about the conditions 
under which alone their life could be led. They 
show that these conditions must be such that in 
the Martian mind there would be one question 
perpetually paramount to all the local labor, 
women's suffrage, and Eastern questions put to- 
gether — the water question. How to procure 
water enough to support life would be the great 
communal problem of the day. 

Were Mars like the Earth, we might well de- 
spair of detecting signs of any Martians for 
some time yet. Across the gulf of space that 
separates us from Mars, an area thirty miles 
wide w^ould just be perceptible as a dot. It 



130 MARS 

would, in such case, be hopeless to look for evi- 
dence of folk. Anything like London or New 
York, or even Chicago in its own estimation, 
would be too small to be seen, so sorry a fig- 
ure does man cut upon the Earth he thinks to 
own. From the standpoint of forty millions of 
miles distance, probably the only sign of his 
presence here would be such semi-artificialities 
as the great grain-fields of the West when their 
geometric patches turned with the changing 
seasons from ochre to green, and then from 
green to gold. By his crops we should know 
him. A tell-tale fact this, for it would be still 
more likely to be the case with Mars. If the 
surface of the planet were cultivated at all, it 
would probably be upon a much more thorough 
plan than is the case with the Earth. Condi- 
tions hold there which would necessitate a much 
more artificial state of things. If cultivation 
there be, it must be cultivation largely depend- 
ent upon a system of irrigation, and therefore 
much more systematic than any we have as 
yet been forced to adopt. 

Now, at this point in our investigation, when 
the broad features of Mars disclose conditions 
which imply irrigation as their organic corol- 
lary, we are suddenly confronted on the planet's 
face with phenomena so startlingly suggestive 
of this very thing as to seem its uncanny pre- 
sentment. Indeed, so amazingly lifelike is their 



CANALS 131 

appearance that, had we possessed our present 
knowledge of the planet's physical condition 
before, we might almost have predicted what 
we see as criterion of the presence of living 
beings. What confronts us is this : — 

When the great continental areas, the reddish- 
ochre portions of the disk, are attentively ex- 
amined in sufficiently steady air, their desert- 
like ground is seen to be traversed by a network 
of fine, straight, dark lines. The lines start 
from points on the coast of the blue-green re- 
gions, commonly well-marked bays, and proceed 
directly to what seem centres in the middle of 
the continent, since most surprisingly they meet 
there other lines that have come to the same 
spot with apparently a like determinate intent. 
And this state of things is not confined to any 
one part of the planet, but takes place all over 
the reddish-ochre regions. 

The lines appear either absolutely straight 
from one end to the other, or curved in an 
equally uniform manner. There is nothing 
haphazard in the look of any of them. Plotting 
upon a globe betrays them to be arcs of great 
circles almost invariably, even the few outstand- 
ing exceptions seeming to be but polygonal 
combinations of the same. Their most instantly 
conspicuous characteristic is this hopeless lack 
of happy irregularity. They are, each and all, 
direct to a degree. 



132 MARS 

The lines are as fine as they are straight. 
As a rule, they are of scarcely any perceptible 
breadth, seeming on the average to be less than 
a Martian degree, or about thirty miles wide. 
They differ slightly among themselves, some 
being a little broader than this ; some a trifle 
finer, possibly not above fifteen miles across. 
Their length, not their breadth, renders them 
visible ; for though at such a distance we could 
not distinguish a dot less than thirty miles in 
diameter, we could see a line of much less 
breadth, because of its length. Speaking gen- 
erally, however, the lines are all of comparable 
width. 

Still greater uniformity is observable in dif- 
ferent parts of the same line ; for each line 
maintains its individual width, from one end of 
its course to the other. Although, at and near 
the point where it leaves the dark regions, some 
slight enlargement seems to occur, after it has 
fairly started on its course, it remains of substan- 
tially the same size throughout. As to whether 
the lines are even on their edges or not, I 
should not like to say ; but the better they are 
seen, the more even they look. It is not possi- 
ble to affirm positively on the point, as they are 
practically nearer one dimension than two. 

On the other hand, their length is usually 
great, and in cases enormous. A thousand or 
fifteen hundred miles may be considered about 



CANALS 133 

the average. The Ganges, for example, which 
is not a long one as Martian canals go, is about 
1,450 miles in length. The Brontes, one of the 
newly discovered, radiating from the Gulf of 
the Titans, extends over 2,400 miles ; while, 
among really long ones, the Eumenides, with 
its continuation the Orcus, the two being in 
truth one line, measures 3,540 miles from the 
point where it leaves the Phoenix Lake to the 
point where it enters the Trivium Charontis, — 
throughout this whole distance, nearly equal to 
the diameter of the planet, deviating neither to 
the right nor to the left from the great circle 
upon which it set out. On the other hand, the 
shortest line is the Nectar, which is only about 
250 miles in length ; sweetness being, according 
to Schiaparelli its christener, as short-lived on 
Mars as elsewhere. 

That, with very few exceptions, the lines all 
follow arcs of great circles is proved, — first, by 
the fact that, when not too long, they show as 
straight lines ; second, that, when seen near 
the limb, they appear curved, in keeping with 
the curvature of a spherical surface viewed 
obliquely ; third, that, when the several parts 
of some of the longer lines are plotted upon a 
globe, they turn out to lie in one great circle. 
Apparent straightness throughout is only possi- 
ble in comparatively short lines. For a very 
long arc upon the surface of a revolving globe 



134 MARS 

tilted toward the observer to appear straight in 
its entirety, it must He due north and south. 
Such, of course, is rarely the case. It so chances, 
however, that these conditions are fulfilled by 
the great canal called the Titan. The Titan 
starts from the Gulf of the Titans, in south lati- 
tude 20°, and runs north almost exactly upon 
the 169th meridian for an immense distance. I 
have followed it over 2,300 miles down the disk 
to about 43° north, as far as the tilt of the 
planet's axis would permit. As the rotation of 
the planet swings it round, it passes the central 
meridian of the disk simultaneously throughout 
its length, and at that moment comes out so 
strikingly straight it seems a substantialized 
meridian itself. 

Although each line is the arc of a great circle, 
the direction taken by this great circle may be 
any whatsoever. The Titan, as we have seen, 
runs nearly due north and south. Certain 
canals crossing this run, on the contrary, al- 
most due east and west. There are others, 
again, belting the disk at well-nigh every angle 
between these two extremes. Nor is there any 
preponderance, apparently, for one direction as 
against any other. This indifference to direc- 
tion is important as showing that the rotation 
of the planet has no bearing upon the inclina- 
tion of the canals. 

But, singular as each line looks to be by it- 



CANALS 135 

self, it is the systematic network of the whole 
that is most amazing. Each line not only goes 
with wonderful directness from one point to 
another, but at this latter spot it contrives to 
meet, exactly, another line which has come with 
like directness from quite a different direction. 
Nor do two only manage thus to rendezvous. 
Three, four, five, and even seven will similarly 
fall in on the same spot, — a gregariousness 
which, to a greater or less extent, finds effec- 
tive possibility all over the surface of the planet. 
The disk is simply a network of such inter- 
sections. Sometimes a canal goes only from 
one intersection to another; more commonly 
it starts with right of continuation, and, after 
reaching the first rendezvous, goes on in un- 
changed course to several more. 

The result is that the whole of the great 
reddish-ochre portions of the planet is cut up 
into a series of spherical triangles of all possible 
sizes and shapes. What their number may be 
lies quite beyond the possibility of count at 
present ; for the better our own air, the more 
of them are visible. About four times as many 
as are down on Schiaparelli's chart of the same 
regions have been seen at Flagstaff. But, be- 
fore proceeding further with a description of 
these Martian phenomena, the history of their 
discovery deserves to be sketched here, since it 
is as strange as the canals themselves. 



136 MARS 

The first hint the world had of their exist- 
ence was when Schiaparelli saw some of the 
lines in 1877, now eighteen years ago. The 
world, however, was anything but prepared for 
the revelation, and, when he announced what 
he had seen, promptly proceeded to disbelieve 
him. Schiaparelli had the misfortune to be 
ahead of his times, and the yet greater misfor- 
tune to remain so ; for not only did no one else 
see the lines at that opposition, but no one 
else succeeded in doing so at subsequent ones. 
For many years fate allowed Schiaparelli to 
have them all to himself, a confidence he amply 
repaid. While others doubted, he went from 
discovery to discovery. What he had seen in 
1877 was not so very startling in view of what 
he afterward saw. His first observations might 
well have been of simple estuaries, long natural 
creeks running up into the continents, and even 
cutting them in two. His later observations 
were too peculiar to be explained, even by so im- 
probable a configuration of the Martian surface. 
In 1879 the canali, as he called them (channels, 
or canals, the word may be translated, and it is 
in the latter sense that he now regards them), 
showed straighter and narrower than they had 
in 1877 : this not in consequence of any change 
in them, but from his own improved faculty of 
detection ; for what the eye has once seen it 
can always see better a second time. As he 



CANALS 137 

gazed they appeared straighter, and he made 
out more. Lastly, toward the end of the year, 
he observed one evening what struck even him 
as a most startUng phenomenon, — the twin- 
ning of one of the canals: two parallel canals 
suddenly showed where but a single one had 
showed before. The paralleling w^as so perfect 
that he suspected optical illusion. He could, 
however, discover none by changing his tele- 
scopes or eye-pieces. The phenomenon, appar- 
ently, was real. 

At the next opposition he looked to see if 
by chance he should mark a repetition of the 
strange event, and went, as he tells us, from 
surprise to surprise; for one after another of 
his canals proceeded startlingly to become two, 
until some twenty of them had thus doubled. 
This capped the climax to his own wonderment, 
and, it is needless to add, to other people's in- 
credulity ; for nobody else had yet succeeded 
in seeing the canals at all, let alone seeing them 
double. Undeterred by the general skepticism, 
he confirmed at each fresh opposition his pre- 
vious discoveries, which, in view of the fact that 
no one else did, tended in astronomical circles 
to an opposite result. 

For nine years he labored thus alone, having 
his visions all to himself. It was not till 1886 
that any one but he saw the canals. In April 
of that year Perrotin, at Nice, first did so. The 



138 MARS 

occasion was the setting up of the great Nice 
glass of twenty-nine inches aperture. In spite 
of the great size of the glass, however, a first 
attempt resulted in nothing but failure. So, 
later, did a second, and Perrotin was on the 
point of abandoning the search for good, when, 
on the 15th of the month, he suddenly detected 
one of the canals, the Phison. His assistant, 
M. Thollon, saw it immediately afterward. After 
this they managed to make out several others, 
some single, some double, substantially as Schia- 
parelli had drawn them ; the slight discrep- 
ancies between their observations and his being 
in point of fact the best of confirmations. 

Since then, other observers have contrived to 
detect the canals, the list of the successful in- 
creasing at each opposition, although even now 
their number might almost be told on one's 
hands and feet. 

The reason that so few astronomers have as 
yet succeeded in seeing these lines is to be 
found in our own atmosphere. That in ordi- 
nary atmosphere the lines are not easy objects 
is certain. A moderately good air is essential 
to their detection ; and unfortunately the loca- 
tions of most of our observatories preclude this 
prerequisite. Size of aperture of the telescope 
used is a very secondary matter. That Schia- 
parelli discovered the canals with an 8J-inch 
glass, and that the 2 6 -inch glass at Washington 



Plate XVIII 




FASTIGIUM ARYN 
October, 1894 



Lowell Observatory 
Flagstaff, A. T. 1894 



CANALS 139 

has refused to show them to this day, are facts 
that speak emphatically on the point. 

The importance of atmosphere in the study 
of planetary detail is far from being appre- 
ciated. It is not simply question of a clear 
air^ but of a steady one. To detect fine detail, 
the atmospheric strata must be as evenly dis- 
posed as possible. 

Next in importance to a steady air comes at- 
tentive perception on the part of the observer. 
The steadiest air we can find is in a state of 
almost constant fluctuation. In consequence, 
revelations of detail come only to those who 
patiently watch for the few good moments 
among the many poor. Nor do I believe even 
average air to be entirely without such happy 
exceptions to a general blur. In these brief 
moments perseverance will show the canals as 
faint streaks. To see them as they are, how- 
ever, an atmosphere possessing moments of 
really distinct vision is imperative. For the 
canals to come out in all their fineness and 
geometrical precision, the air must be steady 
enough to show the markings on the planet's 
disk with the clear-cut character of a steel en- 
graving. No one who has not seen the planet 
thus can pass upon the character of these lines. 

Although skepticism as to the existence of 
the so-called canals has been now pretty well 
dispelled by these and other observations, dis- 



140 MARS 

belief still makes a desperate stand against their 
peculiar appearance, dubbing accounts of their 
straightness and duplication as sensational, what- 
ever they may mean in such connection; for 
that they are both straight and double, as de- 
scribed, is certain, — a statement I make after 
having seen them, instead of before doing so, as 
is the case with the gifted objectors. Doubt, 
however, will not wholly cease till more peo- 
ple have seen them, which will not happen till 
the importance of atmosphere in the study of 
planetary detail is more generally appreciated 
than it is to-day. To look for the canals with 
a large instrument in poor air is like trying to 
read a page of fine print kept dancing before 
one's eyes, with the additional disadvantage 
that increase of magnification increases the mo- 
tion. Advance in our study of other worlds 
depends upon choosing the very best atmos- 
pheric sites for our observatories. 

It is interesting to recall, in connection with 
this incredulity about the canals, that precisely 
the same thing happened in the case of the dis- 
covery of Jupiter's satellites and with Huy- 
ghens' explanation of Saturn's ring. We are 
apt to imagine that our age of the world has a 
monopoly of skepticism. But this is a mistake. 
The spirit that denies has always been abroad ; 
only in early days he was reputed to be the 
devil. 



MAP AND CATALOGUE 141 
II. MAP AND CATALOGUE 

As we shall now have to call these Martian 
things by their names, — our names, that is, — 
it may be well to consider cursorily the nomen- 
clature which has been evolved on the subject. 
Unfortunately, the planet has been quite too 
much benamed, — benamed, indeed, out of all 
recognition. There are no less than five or six 
systems current for its general topographical 
features. The result is that it has become 
something of a specialty just to know the 
names. The Syrtis Major, for example, appears 
under the following aliases : the Syrtis Major, 
the Mer du Sablier, the Kaiser Sea, the North- 
ern Sea, to say nothing of translations of these, 
such as the Hourglass Sea ; after which ample 
baptism it is a trifle disconcerting to have the 
sea turn out, apparently, not to be a sea at all. 
Everybody has tried his hand at naming the 
planet, first and last ; naming a thing being 
man's nearest approach to creating it. Proctor 
made a chart of the planet, and named it 
thoroughly ; Flammarion made another chart, 
and also named it thoroughly, but differently ; 
Green drew a third map, and gave it a third set 
of names ; Schiaparelli followed with a fourth, 
and furnished it with a brand-new set of his 
own ; and finally W. H. Pickering found it 
necessary to give a few new names, just for 



142 MARS 

particiilarization. To know, therefore, what 
part of the planet anybody means when he 
mentions it, one has to keep in his head enough 
names for five worlds. To cap which, it is to 
be remarked that not one of them is the thing's 
real — that is, its Martian — name, after all ! 

Fortunately, with the canals, matters are not 
so desperate, because so few people have seen 
them. Schiaparelli's monopoly of the sight 
pleasingly prevented, in their case, christening 
competition. What is more, he named them, 
very judiciously and most picturesquely, after 
mythologic river names. Where he got his 
names is another matter. Whether he started 
by being as learned in such lore as he afterward 
became may well be doubted. Certainly, one 
of the greatest discoveries made at Flagstaff has 
been the discovery of the meaning of Schiapa- 
relli's names; some of them still defying the 
penetrating power of the ordinary encyclopae- 
dia. Among them are classical mythologic ones 
of the class known only to that himself myth- 
ical character, Macaulay's every schoolboy; 
which speaks conclusively for their recondite- 
ness. Others, I firmly believe, even that om- 
niscient schoolboy can never have heard of. 
Want of space here precludes instances ; but as 
a simple example I may say that the translation 
to Mars of the Phison and the Gihon, the two 
lost rivers of Mesopotamia, satisfactorily ac- 



MAP AND CATALOGUE 143 

counts for their not being found on earth by 
modern explorers. 

With due mental reservation as to their 
meaning, I have adopted Schiaparelli's names, 
and, where it has been necessary to name newly 
discovered canals, have conformed as closely as 
possible to his general scheme. If, even in an 
instance or two, I have hit upon names that are 
incomprehensible, I shall feel that I have not dis- 
graced my illustrious predecessor. For a brand- 
new thing no name is so good as one whose 
meaning nobody knows, except one that has no 
meaning at all. In that case the name not only 
is becoming but actually becomes the thing. 

These names will be found affixed to their 
respective canals in the map at the end of the 
book, a map made upon what is called Merca- 
tor's projection. Mercator's projection I take to 
have been primarily an invention of the devil, 
although commonly credited to Mercator. It is 
not simple to construct and for popular purposes 
is eminently deceitful. It is intended for those 
at sea, whom we pray for on Sundays. It is cer- 
tainly calculated to put any one entirely at sea 
who attempts to learn geography by means of it. 
Its object is to enable such as wish to do so to sail 
upon rhumb lines, a rhumb line upon a sphere 
being one which never changes its direction, — 
one, for example, which runs perpetually north- 
east one quarter east, or south half west. 



144 MAKS 

These lines, important in navigation, are in 
reality diminishing corkscrew-like spirals, but 
on this projection become straight lines which 
can be instantly laid down by rule and compass. 
To make such delineation possible it is neces- 
sary to distort the proportions of every part of 
the map, in increasing divergence toward the 
poles, with the lamentable result that in early 
life we all believed Nova Zembla to be a place 
as big as South America. Nevertheless Merca- 
tor's projection has certain advantages not so 
obvious to the uninitiated, nor requiring special 
mention here. In this connection it is only 
necessary to warn the reader, in the case of a 
geography with which he is not familiar, like 
that of Mars, to remember that the top and 
bottom of the map are drawn upon a scale 
three or four times as large as the middle ; and, 
furthermore, that it is a consequence of Merca- 
tor's projection that arcs of great circles appear 
upon it, not as straight lines, but as curves al- 
ways more or less concave to the equator. For 
relative size of the various features, he will find 
the twelve views from the globe accurate ; but 
for the impressiveness of the great circle char- 
acter of the canals, nothing short of a globe it- 
seK will give him adequate realization. 

The map represents that part of the planet 
lying between latitudes 70° south and about 
40° north. The south circumpolar regions will 



MAP AND CATALOGUE 



145 



be found in the chart of the south pole facing 
page 84. The northern ones were not pre- 
sented to view at the last opposition, owing to 
the tilt toward us of the Martian south pole. 
No canals, therefore, north of about 40° north 
latitude were visible. 

The list of the canals detected at Flagstaff is 
as follows : 



Name. 


No. of drawings in 


Name. 


No. of drawings in 


which it appears. 


which it appears. 


Acalandrus 


19 






Astaboras 


7 


Acampsis 


7 






Astapus 


29 


Acesines 


19 






Atax 


8 (Sus. 1) 


Achana 


1 






Athesis 


16 


Achates 


9 






Avernus 


14 


Achelous 


20 






Avus 


8 


Acheron 


11 






Axius 


9 


Acis 


14 






Axon 


2 


Aeolus 


13 






Bactrus 


2 (Sus. 1) 


Aesis 


23 






Baetis 


3 


Aethiops 


16 






Bathys 


69 


Agathodaemon 


127 






Bautis 


(Sus. 1) 


Alpheus 


4 


(Sus. 


3) 


Belus 


3 


Ambrosia 


36 






Boreas 


11 


Amenthes 


26 






Boreosyrtis 


4 


Amphrysus 


1 






Brontes 


38 


Amystis 


15 






Caicus 


8 


Anapus 


7 






Cambyses 


34 


Antaeus 


2 


(Sus. 


1) 


Cantabras 


7 


Anubis 


9 






Carpis 


3 


Araxes 


93 


(Sus. 


1) 


Casuentus 


21 


Arges 


2 






Catarrhactes 


3 


Arosis 


8 






Cayster 


3 


Arsanias 


1 






Centrites 


27 


Artanes 


9 






Cephissus 


35 


Asopus 


5 






Cerberus 


44 (Sus. 1) 



146 



MAES 



IVTo-ma 


No. of drawings in 


Namt> 


No. of drawings in 


JName. 


which it appears. 


JMame. 


which it appears. 


Oestrus 


2 






Gaesus 


2 


Chaboras 


4 






Galaesus 


6 


Chretes 


14 






Galaxias 


28 


Chrysas 


6 






Ganges 


82 


Chrysorrhoas 


18 






Ganymede 


19 


Cinyphus 


14 






Garrhuenus 


12 


Clitumnus 


7 






Gehon 


11 


Clodianus 


1 






Gigas 


60 (Sus. 2) 


Cophen 


5 






Glaucus 


2 


Coprates 


41 






Gorgon 


33 


Corax 


33 






Gyes 


15 


Cyaneus 


6 






Hades 


22 


Cyrus 


3 






Halys 


4 


Daemon 


118 






Harpasus 


2 


Daix 


2 


(Sus. 


1) 


Hebe 


37 


Daradax 


6 






Helisson 


12 


Dardanus 


15 






Heratemis 


4 


Dargamanes 


20 






Herculis Columnae 5 


Deuteronilus 


11 






Hiddekel 


18 


Digentia 


2 






Hipparis 


19 


Dosaron 


10 






Hippus 


13 


Drahonus 


5 






Hyctanis 


4 


Elison 


3 






Hydaspes 


1 


Eosphorus 


66 


(Sus. 


3) 


Hydraotes 


23 


Erannoboas 


17 






Hydriacus 


1 


Erebus 


21 


(Sus. 


1) 


Hylias 


7 


Erinaeus 


16 






Hyllus 


14 


Erymanthus 


21 






Hyphasis 


7 (Sus. 3) 


Erynnis 


3 


(Sus. 


1) 


Hypsas 


6 


Eulaeus 


1 






Hyscus 


13 


Eumenides 


103 






Indus 


10 


Eunostos 


12 






Iris 


7 


Euphrates 


36 






Isis 


5 


Eurymedon 


3 






Jamuna 


39 


Eurypus 


9 






Jaxartes 


23 


Evenus 


9 






Labotas 


8 


Fortunae 


10 






Laestrygon 


41 



MAP AND CATALOGUE 



147 



Tm&THG. 


No. of drawings in 


Name. 


No. of drawings in 




which it appears. 


which it appears. 


Leontes 


2 


Palamnus 


9 


Lethes 


19 


Parcae 


19 (Sus. 1) 


Liris 


13 


Peneus 


3 (Sus. 2) 


Maeander 


6 


Phasis 


29 


Magon 


2 


Phison 


56 


Malva 


8 


Proton ilus 


11 


Margus 


1 


Psychrus 


5 


Medus 


2 


Pyriphlegethon 


53 (Sus. 1) 


Medusa 


24 


Scamander 


21 


Mogrus 


2 


Sesamus 


7 


Nectar 


87 


Simois 


5 


Neda 


2 


Sirenius 


60 


Nepenthes 


21 


Sitacus 


3 


Nereides 


8 


Steropes 


46 


Nestus 


5 


Styx 


7 


Neudrus 


10 


Surius 


6 


Nilokeras 


16 


Tartarus 


42 


Nilosyrtis 


21 


Tedanius 


25 


Nilus 


6 


Thernaodon 


2 


Nymphaens 


4 


Thyanis 


1 


Oceanus 


37 


Titan 


38 


Ochus 


3 


Tithonius 


77 


Opharus 


13 


Triton 


8 


Orcus 


35 


Tyndis 


2 


Orontes 


33 


Typhon 


33 


Orosines 


29 


Ulysses 


33 


Oxus 


11 


Uranius 


8 


Pactolus 


11 


Xanthus 


12 


Padargus 


5 







The number of canals in this list is 183, and 
the number opposite each denotes the number 
of times each was seen and drawn ; (Sus.) mean- 
ing, suspected in addition. There were in all, 
therefore, 3240 records made of them, not 
counting suspicions. 



148 MARS 

In the region visible at this opposition Schia- 
parelli has 79 canals. Of these 67 appear in the 
list given above. Of the other 12, the majority 
lie north of the equator, and therefore were 
likely not to be as visible as the rest at this last 
opposition, for two reasons connected with their 
position : first, on account of the tilt of the 
planet's axis at the time ; and, secondly, because 
their northern situation would make their de- 
velopment late, as we shall shortly see. As no 
attempt was made to identify Schiaparelli's list, 
it will be seen how close is the accordance. 

Of the 116 canals not down on Schiaparelli's 
map, 44 are canals in the dark regions and 72 
canals in the light ones. Some of these, too, he 
saw prior to 1894. Both sets are, as a rule, 
more difficult of detection than the ones on his 
map; although there are some exceptions, at- 
tributable probably to difficulty of identification. 
The Brontes and Steropes, for example, might, 
unless well seen, be confounded with the Gigas 
on the one hand, or the Titan on the other. 
The most peculiar case, however, is the relative 
conspicuousness of the Ulysses. 

III. ARTIFICIALITY. 

It is patent that here are phenomena that are 
passing strange. To read their riddle we had 
best begin by excluding what they are not, as 
help towards deciphering what they are. 



ARTIFICIALITY 149 

So far, we have regarded the canals only 
statically, so to speak ; that is, we have sketched 
them as they would appear to any one who ob- 
served them in sufficiently steady air, once, and 
once only. But this is far from all that a sys- 
tematic study of the lines will disclose. Before, 
however, entering upon this second phase of 
their description, we may pause to note how, 
even statically regarded, the aspect of the lines 
is enough to put to rest all the theories of 
purely natural causation that have so far been 
advanced to account for them. This negation 
is to be found in the supernaturally regular ap- 
pearance of the system, upon three distinct 
counts : first, the straightness of the lines ; 
second, their individually uniform width ; and, 
third, their systematic radiation from special 
points. 

On the first two counts we observe that the 
lines exceed in regularity any ordinary regu- 
larity of purely natural contrivance. Physical 
processes never, so far as we know, end in pro- 
ducing perfectly regular results ; that is, results 
in which irregularity is not also discernible. 
Disagreement amid conformity is the inevitable 
outcome of the many factors simultaneously at 
work. From the orbits of the heavenly bodies 
to phyllotaxis and human features, this diversity 
in uniformity is apparent. As a rule, the di- 
vergences, though small, are quite perceptible ; 



150 MARS 

that is, the lack of absolute uniformity is com- 
parable to the uniformity itself, and not of the 
negligible second order of unimportance. In 
fact, it is by the very presence of uniformity 
and precision that we suspect things of artifi- 
ciality. It was the mathematical shape of the 
Ohio mounds that suggested mound-builders; 
and so with the thousand objects of e very-day 
life. Too great regularity is in itself the most 
suspicious of circumstances that some finite in- 
telligence has been at work. 

If it be asked how, in the case of a body so 
far off as Mars, we can assert sufficient precision 
to imply artificiality, the answer is twofold : 
first, that the better we see these lines, the 
more regular they look ; and, second, that the 
eye is quicker to perceive irregularity than we 
commonly note. It is indeed surprising to find 
what small irregularities will shock the eye. 

The third count is, if possible, yet more con- 
clusive. That the lines form a system ; that, 
instead of running any whither, they join cer- 
tain points to certain others, making thus, not a 
simple network, but one whose meshes connect 
centres directly with one another, — is striking 
at first sight, and loses none of its peculiarity 
on second thought. For the intrinsic improb- 
ability of such a state of things arising from 
purely natural causes becomes evident on a 
moment's consideration. 



AETIFICIALITY 151 

If lines be drawn haphazard over the sur- 
face of a globe, the chances are ever so many 
to one against more than two lines crossing each 
other at any point. Simple crossings of two 
lines will of course be common in something like 
factorial proportion to the number of lines ; but 
that anv other line should contrive to cross at 
the same point would be a coincidence whose im- 
probability only a mathematician can properly 
appreciate, so very great is it. If the lines 
were true lines, without breadth, the chances 
against such a coincidence would be infinite, 
that is, it would never happen ; and, even had 
the lines some breadth, the chances would be 
enormous against a rendezvous. In other words, 
we might search in vain for a single instance of 
such encounter. On the surface of Mars, how- 
ever, instead of searching in vain, we find the 
thing occurring passim ; this a priori most im- 
probable rendezvousing proving the rule, not 
the exception. Of the crossings that are best 
seen, all are meeting-places for more than two 
canals. 

To any one who had not seen the canals, it 
might occur that something of the same improb- 
ability would be fulfilled by cracks radiating 
from centres of explosion or fissure. But such a 
supposition is at once negatived by the uniform 
breadth of the lines, a uniformity impossible in 
cracks, whose very mode of production necessi- 



152 MARS 

tates their being bigger at one end than at the 
other. We see examples of what might result 
from such action in the cracks that radiate from 
Tycho, in the Moon, or^ as we now know from 
Professor W. H. Pickering's observations, from 
the craterlets about it. These cracks bear no 
resemblance whatever to the lines on Mars. 
They look like cracks ; the lines on Mars 
do not. Indeed, it is safe to say that the 
Martian lines would never so much as suggest 
cracks to any one. Lastly, the different radia- 
tions fit into one another absolutely, an utter 
impossibility were they radiating rifts from dif- 
ferent centres. 

In the same way we may, while we are about 
it, show that the lines cannot be several other 
things which they have more or less gratui- 
tously been taken to be. They cannot, for ex- 
ample, be rivers ; for rivers could not be so obli- 
gingly of the same size at source and mouth, nor 
would they run from preference on arcs of great 
circles. To do so, practically invariably, would 
imply a devotion to pure mathematics not com- 
mon in rivers. They may, in some few in- 
stances, be rectified rivers, which is quite 
another matter. Glaciation cracks are equally 
out of the question, — first, for the causes above 
mentioned touching cracks in general; and, 
second, because there is, unfortunately, no ice 
where they occur. Nor can the lines be fur- 



ARTIFICIALITY 153 

rows ploughed by meteorites, — another ingen- 
ious suggestion, — since, in order to plough, 
invariably, a furrow straight from one centre to 
another, without either missing the mark or 
overshooting it, the visitant meteorite would 
have to be specially trained to the business. 

Such are the chief purely natural theories of 
the lines, excluding the idea of canals, — the- 
ories advanced by persons who have not seen 
them. No one who has seen the lines well 
could advance them, inasmuch as they are not 
only disproved by consideration of the char- 
acter of the lines, but instantly confuted by the 
mere look of them. 

Schiaparelli supposes the canals to be canals, 
but of geologic construction. He suggests, how- 
ever, no explanation of how this is possible ; so 
that the suggestion is not, properly speaking, 
a theory. That eminent astronomer further 
says of the idea that they are the work of intel- 
ligent beings : " lo mi guardero bene dal com- 
battere questa supposizione, la quale nulla 
include d' impossibile." (I should carefully re- 
frain from combating this supposition, which 
involves no impossibility.) In truth, no natural 
theory has yet been advanced which will ex- 
plain these lines. 

Their very aspect is such as to defy natural 
explanation, and to hint that in them we are 
regarding something other than the outcome of 



154 MARS 

purely natural causes. Indeed, such is the first 
impression upon getting a good view of them. 
How instant this inference is becomes patent 
from the way in which drawings of the canals 
are received by incredulously disposed persons. 
The straightness of the lines is unhesitatingly 
attributed to the draughtsman. Now this is a 
very telling point. For it is a case of the 
double-edged sword. Accusation of design, if 
it prove not to be due to the draughtsman, 
devolves ipso facto upon the canals. 

IV. DEVELOPMENT 

We have thus far considered the aspect of 
the canals viewed at any one time. We have 
now to consider an even more interesting 
branch of the subject, their consecutive appear- 
ances. The " open sesame " to our comprehen- 
sion of the physical condition of Mars lies in 
systematic study of the appearances the planet's 
surface presents night after night and month 
after month. For that surface changes ; and 
the order, extent, and character of its changes 
contain the key to their explanation. True as 
this is of the larger markings upon the disk, it 
is if anything more noticeably the case with the 
finer detail of the canals. 

After the fundamental fact that such curious 
phenomena as the canals are visible, is the 
scarcely less curious one that they are not 



DEVELOPMENT 155 

always so. At times the canals are invisible, 
and this invisibility is real, not apparent; that 
is, it is not an invisibility due to distance or 
obscuration of any kind between us and them, 
but an actual invisibility due to the condition 
of the canal itself. With our present optical 
means, at certain seasons they cease to exist. 
For aught we can see, they simply are not 
there. 

That distance is not responsible for the disap- 
pearance of the canals is shown by their relative 
conspicuousness at different times. It is not 
always when Mars is nearest to us that the 
canals are best seen. On the contrary, their 
visibility bears no relation to proximity. This 
is evidenced both by the changes in appear- 
ance of any one canal and by the changes 
in relative conspicuousness of different canals. 
Some instances of the metamorphosis will re- 
veal this conclusively. For example, during 
the end of August and the beginning of Sep- 
tember, at this last opposition, the canals about 
the Lake of the Sun were conspicuous, while 
the canals to the north of them were almost 
invisible. In November the relative intensities 
of the two sets had distinctly changed : the 
southern canals were much as before, but the 
northern ones had most perceptibly darkened. 

Another instance of the same thing was 
shown in the case of the canals to the north of 



156 MARS 

the Sinus Titaniim when compared with those 
about the Sohs Lacus. In August the former 
were but faintly visible ; in November they had 
become evident; and yet, during this interval, 
little change in conspicuousness had taken place 
in the canals in the Solis Lacus region. 

With like disregard of the effect due to dis- 
tancCj the canals to the east of the Ganges 
showed better at the November presentation^ of 
that region than they had at the October one, 
although the planet was actually farther off at 
the later date, in the proportion of 21 to 18. 

A more striking instance of the irrelevancy 
of distance in the matter was observed in the 
same region by Schiaparelli in 1877. It is ad- 
ditionally interesting as practically dating his 
discovery of the canals. In early October of 
that year, on the evenings of the 2d and the 
4th, he tells us, under excellent definition, and 
with the diameter of the planet's disk 21'^ of 
arc, the continental region between the Pearl- 
Bearing Gulf and the Bay of the Dawn was 
quite uniformly, nakedly bright, and destitute 

^ A presentation of any part of the planet is the occasion 
when that part of the disk is turned toward the observer. Many 
causes combine to make the face presented each night vary, but 
the chief one is that the Earth rotates about forty-one minutes 
faster than Mars, and consequently gains a little less than ten de- 
grees on him daily. After about thirty-seven days, therefore, 
the two planets again present the same face to each other at the 
same hour. 



DEVELOPMENT 157 

of suspicion of markings of any sort. A like 
state of things was the case with the same re- 
gion at its next presentation, on the 7th of 
November. Four months later, when the di- 
ameter of the disk had been reduced by dis- 
tance to 5''. 7, or, in other words, when the 
planet had receded to four times its previous 
distance from the earth, the canal called the 
Indus appeared, perfectly visible, in the region 
mentioned. At the next opposition, in 1881, 
similar effects occurred ; the canals in this re- 
gion remaining obstinately invisible while the 
planet was near the earth, and then coming out 
conspicuously when it had gone farther away. 
Distance, therefore, is not, with the canals, the 
great obliterator. 

As to their veiling by Martian cloud or mist, 
there is no evidence of any such obscuration. 
The coast line of the dark areas appears as 
clear-cut when the canals are invisible as when 
they become conspicuous. 

A canal, then, alters in visibility for some 
reason connected with itself. It grows into 
recognition from intrinsic cause. But, during 
all its metamorphoses, in one thing, and in one 
thing only, it remains fixed, — in position. 
Temporary in appearance, the canals are appar- 
ently permanent in place. Not only do they 
not change in position during one opposition ; 
they seem not to do so from one opposition to 



158 MARS 

another. The canals I have observed this year 
agree fairly within the errors of observation 
with those figured on Schiaparelli's chart. 

The fact that in all cases they do not abso- 
lutely agree with his is the very best of proofs 
that they are substantially the same ; for such 
slight discordance proves the absence of con- 
scious psychic reproduction. It confirms by 
not conforming. 

As, in observations of minute detail, the 
psychic element insensibly creeps in, it will be 
well to consider it for a moment. An idea is 
a force, a mode of motion, which, unless ob- 
structed by other ideas, instantly and inevitably 
produces its effect upon whatever mind it may 
chance to impinge, just as light or electricity or 
any other mode of motion does, according to its 
kind. An easy instance of this can be got by 
asserting at dinner, before a company of con- 
noisseurs, that the wine is slightly corked. 
Every one not actuated by a spirit of contradic- 
tion will at once perceive that it is so, and will 
continue to believe it, in many cases, after it is 
abundantly disproved. This is what takes place 
in the normal, unbiased — that is, so far as this 
idea goes — vacant mind. But minds have their 
familiar ideas, which an incoming idea is pretty 
sure to rouse, and these react to some extent 
upon the stranger, and color it with something 
of their own complexion. If we expect to meet 



DEVELOPMENT 159 

a certain person, an approaching figure will 
most deceitfully take on his garb. The mere 
idea of a man walking finds the expectation 
ready instinctively to endow it with the attri- 
butes of our friend. But this may happen 
truly as well as falsely. The expert sees what 
the tyro misses, not from better eyesight but 
from better mechanism in the higher centres. 
A very slight hint from the eye goes a long 
way in the brain of the one ; no distance at all 
in the brain of the other. 

Our senses are our avenues of approach from 
the outer world. Messages from them are 
therefore usually and rightly attributed to 
stimuli from without. But it is possible for 
these messages to be tampered with at any 
stage of their journey. It is even possible for 
them to be started in some other part of the 
brain, travel down to the lower centres and be 
sent up from them to the higher ones, indistin- 
guishable from bona fide messages from with- 
out. Bright points in the sky or a blow on the 
head will equally cause one to see stars. In the 
first case the eyes were duly affected from 
without ; in the second, the nerves were tapped 
to the same effect in mid-route ; but in each 
case the subsequent current travels to the 
higher centres apparently as authentic the one 
as the other. 

Hallucinations of one sort and another occur 



160 MARS 

in this way. More common, however, are un- 
conscious changes in an originally quite veridic 
message. We easily see what we expect to see, 
but with great difficulty what we do not. This 
may be due to individual idiosyncrasy, or it may 
be due to a prevailing idea of the time, affecting 
people generally, in which we unwittingly share. 
Fashion is as potent here as elsewhere. The 
very same cause will show us at one time what 
we remain callously blind to at another. A 
few years ago it was the fashion not to see the 
canals of Mars, and nobody except Schiaparelli 
did. Now the fashion has begun to set the 
other way, and we are beginning to have pre- 
sented suspiciously accurate f ac-similes of Schia- 
parelli' s observations. 

In any observation, the observer is likely to 
be unconsciously affected in some way or other 
'pro or con, which, from the fact that he is un- 
conscious of it, he is unable to find out. The 
only sure test, therefore, is the seeing what no 
one else has seen, the discovery of new detail. 
Next to that is not too close an agreement with 
others. Inevitable errors of observation, to say 
nothing of times and seasons, distance and tilt, 
are certain to produce differences, of which one 
has ample proof in comparing his own drawings 
with one another. Even too close agreement 
with one's self is suspicious. In the matter 
of fine detail, absolute agreement is therefore 
neither to be expected nor to be desired. 



DEVELOPMENT 161 

All the changes so far observed on the 
planet's disk are, I believe, capable of explana- 
tion either by errors of observation or by sea- 
sonal change. For, as is the case with the 
Earth, not only must vegetation produce differ- 
ent appearances according to the time of year, 
but its aspects would vary somewhat as between 
year and year. This seasonal variation would 
affect not only the visibility of any one canal at 
any particular time, but might easily produce 
apparent alterations of place ; visibility of one 
canal, combined with visibility or invisibility in 
its neighbors, being competent to simulate any 
shift. 

The Araxes is a case in point. On Schiapa- 
relli's chart there is but one original Araxes 
and one great and only Phasis. But it turns 
out that these do not possess the land all to 
themselves. No less than five canals traversing 
the region, including the Phasis itself, were vis- 
ible this year at Flagstaff, and I have no doubt 
there are plenty of others waiting to be dis- 
covered. These cross one another at all sorts 
of angles. Unconscious combination of them is 
quite competent to give a turn to the Araxes 
one way or the other, and make it curved or 
straight at pleasure. 

Unchangeable, apparently, in position, the 
canals are otherwise among the most change- 
able features of the Martian disk. From being 



162 MARS 

invisiblej they emerge gradually, for some rea- 
son inherent in themselves, into conspicuous- 
ness. In short, phenomenally at least, they 
grow. The order of their coming carries with 
it a presumption of cause, for it synchronizes 
with the change in the Martian seasons. Their 
first appearance is a matter of the Martian time 
of year. 

To start with, the visible development of the 
canal system follows the melting of the polar 
snows. Not until such melting has progressed 
pretty far do any of the canals, it would seem, 
become perceptible. 

Secondly, when they do appear, it is, in the 
case of the southern hemisphere, the most 
southern ones that become visible first. Last 
June, when the canals were first seen, those 
about the Lake of the Sun and the Phoenix 
Lake were easier to make out than any of the 
others. Now^, this region is the part of the 
reddish-ochre continent, as we may call it, that 
lies nearest the south pole. It extends into 
the blue-green regions as far south as 40° of 
south latitude. Nor do any so-called islands — 
that is, smaller reddish-ochre areas — stand be- 
tween it and the pole. It lies first exposed, 
therefore, to any water descending toward the 
equator from the melting of the polar cap. 

Having once become visible, these canals re- 
mained so, becoming more and more conspicu- 



Plate XIX 




LACUS PHOENICIS 
November, 1894 



Lowell Obsekvatorv 
Flagstaff, A. T. 1894 



DEVELOPMENT 163 

ous as the season advanced. By August they 
had darkened very perceptibly. As yet, those 
in other parts of the planet were scarcely more 
visible than they had been two months before. 
Gradually, however, others became evident, far- 
ther and farther north, till by October all the 
canals bordering the north coast of the dark 
regions were recognizable ; after which the lat- 
ter, in their turn, proceeded to darken, — a state 
of things which continued up to the close of 
observations. (Plates XXI. and XXII.) 

The order in which the canals came out 
hinted that two factors were operative to the 
result, — latitude and proximity to the dark re- 
gions. Other things equal, the most southern 
ones showed first ; beginning with the Solis 
Lacus region, and continuing with those about 
the Sea of the Sirens and the Titan Gulf, and 
so northward down the disk. Other things were 
not, however, always equal in the way of topo- 
graphical position. Notably was this the case 
with the areas to the west of the Syrtis Major, 
which developed canals earlier than their lati- 
tudes would warrant. Now, to the Syrtis Major 
descend from the pole the great straits spoken 
of before, which, although not in their entirety 
water, are probably lands fertilized by a thread 
of water running through them. They connect 
the polar sea with the Syrtis Major in a toler- 
ably straight line. 



164 MAES . 

The direction of the canal also affects its time 
of appearance, though to a less extent. Canals 
running north and south, such as the Gorgon, 
the Titan, the Brontes, and the like, became 
visible, as a rule, before those running east 
and west. Especially was this noticeable in the 
more northern portions of the disk. Time of 
appearance was evidently a question of latitude 
tempered by ease of communication. 

After the canals had appeared, their relative 
intensities changed with time, and the change 
followed the same order in which the initial 
change from invisibility to visibility had taken 
place. A like metamorphosis happened to each 
in turn from south to north, in accordance with, 
and continuance of, the seasonal change that 
affected all the blue-green areas. 

To account for these phenomena, the expla- 
nation that at once suggests itself is, that a 
direct transference of water takes place over 
the face of the planet, and that the canals are 
so many waterways. This explanation labors 
under the difficulty of explaining nothing. 
There are two other objections to it : an insuf- 
ficiency of water, and a superabundance of time, 
for some months elapsed between the apparent 
departure of the water from the pole and its 
apparent advent in the equatorial regions ; fur- 
thermore, each canal did not darken all at once, 
but gradually. We must therefore seek some 



DEVELOPMENT 165 

explanation which accounts for this delay. Now, 
when we do so, we find that the explanation ad- 
vanced above for the blue-green areas explains 
also the canals, namely, that what we see in both 
is, not water, but vegetation ; for if the dark- 
ening be due to vegetation, time must elapse 
between the advent of the water and its per- 
ceptible effects, — time sufficient for the flora to 
sprout. If, therefore, we suppose what we call 
a canal to be, not the canal proper, but the 
vegetation along its banks, the observed phe- 
nomena stand accounted for. This suggestion 
was first made some years ago by Professor W. 
H. Pickering. 

That what we see is not the canal proper, but 
the line of land it irrigates, disposes incidentally 
of the difficult}^- of conceiving a canal several 
miles wide. On the other hand, a narrow, fer- 
tilized strip of country is what we should expect 
to find ; for, as we have seen, the general phys- 
ical condition of the planet leads us to the con- 
ception, not of canals constructed for waterways, 
— like our Suez Canal, — but of canals dug for 
irrigation purposes. We cannot, of course, be 
sure that such is their character, appearances 
being often highly deceitful ; we can only say 
that, so far, the supposition best explains what 
we see. Further details of their development 
point to this same conclusion. 

In emerging from invisibility into evidence. 



166 MARS 

the canals first make themselves suspected, 
rather than seen, as broad, faint streaks smooch- 
ing the disk. Such effect, however, seems to be 
an optical illusion, due to poor air and the diffi- 
culty inherent in detecting fine detail ; for on 
improvement in the seeing I have observed 
these broad streaks contract to fine lines, not 
sensibly different in width from what they 
eventually become. 

The parts of the canals which are nearest the 
dark areas show first, the line extending some- 
times for a few hundred miles into the conti- 
nent, sometimes for a thousand or more ; then, 
in course of time, the canal becomes evident 
in its entirety. Complete visibility takes place 
soon after the canal has once begun to show, 
although it show but faintly throughout. 

This tendency to being seen in toto is more 
strikingly displayed after a canal has attained 
its development. It is then not commonly seen 
in part. Either it is not seen at all, owing to 
the seeing not being good enough, or it is visi- 
ble throughout its length from one junction to 
another. 

Apart from their extension, the growth of the 
canals consists chiefly in depth of tint. They 
darken rather than broaden, — a fact which 
tends to corroborate their vegetal character; 
for that long tracts of country should be thus 
simultaneously flooded all over to a gradually 



DEVELOPMENT 167 

deepening extent is highly iinhkely. while a 
growth of vegetation would deepen in appear- 
ance in precisely the way in which the darken- 
ing takes place. 

As for color, the lines would seem to be of 
the same tint as the blue-green areas. But, 
owing to their narrowness, this is only an infer- 
ence. I have never chanced to see them of 
distinctive color. 

At this point it is probable that a certain ob- 
stacle to such wholesale construction of canals, 
however, will arise in the mind of the reader, 
namely, the thought of mountains ; for moun- 
tains are by nature antagonistic to canals. Only 
the Czar of all the Kussias — if we are to credit 
the account of the building of the Moscow rail- 
way — would be capable of running a canal re- 
gardless of topography. Nor will the doings 
at our own antipodes help us to conceive such 
construction ; for though the Japanese irrigate 
hillsides, the water in the case comes from slopes 
higher yet, whereas on Mars it does not. 

Indeed, for the lines to contain canals we 
must suppose either that mountains prove no 
obstacles to the Martians, or else that there 
are practically no mountains on Mars. For the 
system seems sublimely superior to possible ob- 
structions in the way ; the lines running, appar- 
ently, not where they may, but where they 
choose. The Eumenides-Orcus, for example, 



168 MARS 

pursues the even tenor of its unswerving course 
for nearly 3500 miles. Now, it might be pos- 
sible so to select one's country that one canal 
should be able to do this ; but that every 
canal should be straight, and many of them 
fairly comparable with the Eumenides-Orcus in 
length, seems to be beyond the possibility of 
contrivance. 

In this dilemma between mountains on the 
one hand and canals on the other, a certain 
class of observations most opportunely comes to 
our aid ; for, from observations which have 
nothing to do with the lines, it turns out 
that the surface of the planet is, in truth, most 
surprisingly flat. How this is known will most 
easily be understood from a word or two upon 
the manner in which astronomers have learnt 
the height of the mountains in the Moon. 

The heights of the lunar mountains are found 
from measuring the lengths of the shadows they 
cast. As the Moon makes her circuit of the 
Earth, a varying amount of her illuminated sur- 
face is presented to our view. From a slender 
sickle she grows to full moon, and then dimin- 
ishes again to a crescent. The illuminated por- 
tion is bounded by a semicircle on the one side, 
and by a semi-ellipse on the other. The semi- 
circle is called her limb, the semi-ellipse her 
terminator. The former is the edge we see be- 
cause we can see no farther ; the latter, the 



DEVELOPMENT 169 

line upon her surface where the sun is just ris- 
ing or setting. Now, as we know, the shadows 
cast at sunrise or sunset are very long, much 
longer than the objects that cast them are high. 
This is due to the obliquity at which the light 
strikes them ; the same effect being produced 
by any sufficiently oblique light, such as an 
electric light at a distance. Imperceptible in 
themselves, the heights become perceptible by 
their shadows. A road illuminated by a distant 
arc light gives us a startling instance of this; 
the smooth surface taking on from its shadows 
the look of a ploughed field. 

It is this indirect kind of magnification that 
enables astronomers to measure the lunar moun- 
tains, and even renders such vicariously visible 
to the naked eye. Every one has noticed how 
ragged and irregular the inner edge of the Moon 
looks, while her outer edge seems perfectly 
smooth. In one place it will appear to project 
beyond the perfect ellipse, in another to recede 
from it. The first effect is due to mountain tops 
catching the sun's rays before the plains about 
them ; the other, to mountain tops further ad- 
vanced into the lunar day, whose shadows still 
shroud the valleys at their feet. Yet the ele- 
vations and depressions thus rendered so notice- 
able vanish in profile on the limb. 

Much as we see the Moon with the naked eye 
do we see Mars with the telescope. Mars being 



170 MARS 

outside of us with regard to the Sun, we never 
see him less than half illumined, but we do see 
him with a disk that lacks of being round, — 
about what the Moon shows us when two days 
off from full. It is when he is in quadrature — 
that is, a quarter way round the celestial circle 
from the Sun — that he shows thus, and we 
see him then with the telescope at closer range 
than we ever see the Moon without it. So ob- 
served we notice at once that his terminator, or 
inner edge, presents a very different appearance 
from the lunar one. Instead of looking like a 
saw, it looks comparatively smooth, like a knife. 
From this we know that, relatively to his size, 
he has no elevations or depressions upon his sur- 
face comparable to the lunar peaks and craters. 
His terminator, however, is not absolutely 
perfect. Irregularities are to be detected in it, 
although much less pronounced than those of 
the Moon. His irregularities are of two kinds. 
The first, and by all odds the commonest pheno- 
menon, consists in showing himself on occasions 
surprisingly flat ; not in this case an inferable 
flatness, bilt a perfectly apparent one. In other 
words, his terminator does not show as a semi- 
ellipse, but as an irregular polygon. It looks 
as if in places the rind had been pared off. The 
peel thus taken from him, so to speak, is from 
twenty to forty degrees wide, according to the 
particular part of his surface that shows upon 
the terminator at the time. 



Plate XX 




itJi 24>n 13/1 T,ojn 16/1 15W 16/1 23;;/ j6/i 56;« 17/2 ^ovi 

TERMINATOR VIEWS 

By Prof. W. H, Pickering 

August 24, 1894 

A series of iimistially marked elevations and depressions upon the 
terminator at the above hours 



Lowell Observatory 
Flagstaff, A. T. 1894 



Plate XXI 




Fig. I. Nov. 26. Long. cent. 314 
Seeing 2 to 6. Diam. 15". 8 



Fig. II. Oct. 9. Long. cent. 45° 
Seeing 5 to 9. Diam. 2i".7 




Fig. hi. Feb. 8. Long. cent. 295° 
Seeing 2 to 5. Diam. f.s 



Fig. IV. Nov. 23. Long. cent. 31 
Seeing 2 to 7. Diam. i6/'.3 




Fig. V. March 16. Long. cent. 312'^ 
Seeing 2 to 8. Diam. 6". 4 



Fig. VI. March 9. Long. cent. 26° 
Seeing 3 to 7. Diam. 6" .6 



DRAWINGS AFTER OPPOSITION [except one] 
By a. E. Douglass 



Lowell Observatory 
Flagstaff, A. T. 1895 



DEVELOPMENT 171 

The other kind is short and sharp. Now it 
will be remembered that we considered both 
kinds under the question of atmosphere, and we 
found both to be explicable as the effect of 
clouds, but not the effect of mountains. We 
may therefore feel tolerably certain that Mars 
is a flat world ; devoid, as we may note inciden- 
tally, of summer resorts, since it possesses, ap- 
parently, neither seas nor hills. To canals we 
will now return. 

The canals so far described all lie in the 
bright reddish-ochre portions of the disk, — 
those parts which bear every appearance of 
being desert. But Mr. Douglass has made the 
discovery that they are not the only part of the 
planet thus privileged. He finds, in the very 
midst of the dark regions themselves, straight, 
dark streaks not unlike in look to the canals, 
and still more resembling them in the systematic 
manner in which they run. For they reproduce 
the same rectilinear arrangement that is so 
striking a characteristic of their bright-area 
fellows. He has succeeded, indeed, in thus tri- 
angulating all the more important dark areas. 

Now this is a very interesting discovery, from 
several points of view. In the first place, it 
proves another tell-tale, circumstance as to the 
true character of the so-called seas ; for that the 
seas should be traversed by permanent dark lines 
is incompatible with a fluid constitution. But 



172 MARS 

the lines are even more suggestive from a posi- 
tive than they are from a negative standpoint. 
For they make continuations of the hues in the 
bright regions, showing that the two are caus- 
ally connected, and affording strong presump- 
tion that this causal relation is the very one de- 
manded by the theory of irrigation. For if the 
canals in the bright regions be strips of vegeta- 
tion irrigated by a canal (too narrow to be itself 
visible at our distance), and there be a scarcity 
of water upon the surface of the planet, the 
necessary water would have to be conducted to 
the mouths of the canals across the more per- 
manent areas of vegetation, thus causing bands 
of denser verdure athwart them, which we 
should see as dark lines upon the less dark 
background. Indeed, it is exactly what we 
should expect to find if the theory here ad- 
vanced be true. For it is the very next logical 
step in that theory made visible. If the canals 
in the bright regions are to be fed from the 
melting of the polar cap, it is altogether likely 
that they would be connected with it by other 
canals running through the dark regions. We 
might, therefore, expect to see lines in the dark 
regions not unlike the lines in the bright ones, 
and if these lines were of the same character as 
those in the bright regions they would betray 
this character by connecting directly with them. 
Now this is precisely what he finds the two sets 



Plate XXII 




Fig. I. Nov. 14. 
Seeing 4 to 8. 



Long. cent. 114° 
Diam. 17". 9 



Fig. IL Nov. 5. Long. cent. 184"^ 
Seeing i to 3. Diam. ig".5 




Fig. IIL Dec. 17. Long. cent. 100° 
Seeing 2 to 6. Diam. 12'/. 4 



Fig. IV. Dec. i. 
Seeing 2 to 4. 



Long. cent. 246° 
Diam. 14". 9 




Fig. V. Feb. 21. Long. cent. 193^ 
Seeing 2 to 4. Diam. 7^.4 



Fig. VI. Jan. 8. Long. cent. 266° 
Seeing i to 3. Diam. 9".9 



DRAWINGS AFTER OPPOSITION 
By a. E. Douglass 



Lowell Observatory 
Flagstaff, A. T. 1895 



DEVELOPMENT 



173 



of lines do. His canals in the dark regions end 
at the very points at which the others begin, 
and they do this invariably. There is no canal 
in the dark areas which does not so connect 
with one in the bright regions. 

Finally, some of the most southern appear to 
run tolerably straight toward the pole ; but of 
the plan underlying the whole system of Martian 
canals we cannot at present predicate details, 
as, though the system instantly suggests plan, it 
suggests a plan that does not instantly commend 
itself to human comprehension. 

Mr. Douglass finds 44 of these canals, not 
including the straits between the islands, as is 
shown in the following list : — 



XTnw./^ 


No. of drawings in 




No. of drawings in 


Name. 


whicli it appears. 


Name. 


which it appears. 


Acalandrus 


19 


Dosaron 


10 


Acesines 


19 


Drahonus 


5 


Acis 


14 


Erannoboas 


17 


Aeolus 


13 


Erymanthus 


21 


Amphrysus 


1 


Eurypus 


9 


Athesis 


16 


Gaesus 


2 


Caicus 


8 


Galaesus 


6 


Carpis 


3 


Garrhuenus 


12 


Casuentus 


21 


Harpasus 


2 


Cayster 


3 


Helisson 


12 


Oestrus 


2 


Heratemis 


4 


Chaboras 


4 


Hipparis 


19 


Cinyphus 


14 


Hippus 


13 


Cyaneus 


6 


Hyctanis 


4 


Cyrus 


3 


Hydriacus 


1 


Dargamanes 


20 


Hylias 


7 


Digentia 


2 


Hyllus 


14 



174 



MARS 



Name. 

Leontes 


No. of drawings in 
which it appears. 

2 


Name. 

Oceanus 


No. of drawings in 
which it appears. 

37 


Malva 


8 


Opharus 


13 


Mogrus 

Nestus 

Neudrus 


2 

5 

10 


Orosines 

Padargus 

Tedanius 


29 

5 

25 



All these run either through the dark regions 
proper, or through those chiaro-oscuro areas, 
such as Deucalionis Regio and Pyrrhae Regio, 
which have hitherto been thought to be amphi- 
bious, and are probably half desert. They con- 
nect on the one hand with the canals in the 
bright regions, and on the other with the straits 
between the so-called islands, — such strait- 
canals as Scamander, Xanthus, and the like, if 
we may so designate without misunderstanding 
what is probably not water at all. 

It is interesting thus to forestall objection 
about a missing link by discovering that link 
thus early. 

Before passing on to certain other pheno- 
mena connected with the canals of like signifi- 
cance, we may note here an obiter dictum of the 
irrigation theory of some slight corroborative 
worth; for, if a theory be correct, it will not 
only fit all the facts, but at times go out of its 
way to answer questions. Such the present 
one seems to do. If the seas be seas, and the 
canals canals, we stand confronted by the prob- 
lem how to make fresh-water canals flow out of 



DEVELOPMENT 175 

salt-water seas. General considerations warrant 
us in believing that the Martian seas, like our 
own, would contain salts in solution, while irri- 
gation ditches, there as here, should flow fresh 
water to be most effective, and we seem com- 
mitted to the erection of distilleries upon a 
gigantic scale. But if, on the contrary, the 
seas be not seas, but areas of vegetation, the 
difficulty vanishes at once ; for, if the planet be 
dependent upon the melting of its polar snows 
for its spring freshet, the water thus produced 
must necessarily be fresh, and the canals be 
directly provided with the water they want. 
The polar sea is a temporary body of water, 
formed anew each year, not a permanent ocean ; 
consequently there is no chance for saline mat- 
ter to collect in it. From it, therefore, fresh 
water flows, and, like our rivers, gathers nothing 
to speak of in the way of salt before it is drawn 
off into the canals. 

We now come to some phenomena connected 
with the canals, of the utmost suggestiveness. 
I have said that the junctions held, in a twofold 
way, the key to the unlocking of the mystery 
of the canals : in the first place, in the fact that 
such junctions exist. The second and more im- 
portant reason remains to be given, for it con- 
sists in what we find at those junctions. This 
we shall see in the next chapter. 



V 

OASES 
I. SPOTS IN THE LIGHT EEGI0:N'S 

Suggestive of irrigation as the strange net- 
work of lines that covers the surface of Mars 
appears to be, the suggestion takes on more 
definite shape yet with the last addition to our 
knowledge of the planet's surface detail, — the 
recognition of a singularly correlated system of 
spots. 

The canals, as we have seen, are very re- 
markably attached to one another. Indeed, the 
manner with which they manage to combine 
unde viating direction with meetings by the way 
grows more and more marvelous, the more one 
studies it. The meeting-places, or junctions, 
are evidently for something in the constitution 
of the canals. The crossings, in fact, seem to 
be the end and aim of the whole system ; the 
canals, but means to that end. So much is at 
once inferable from the great intrinsic improba- 
bility that such crossings can be due to chance. 

This inference receives, apparently, striking 
corroboration when the planet is more minutely 



SPOTS IN THE LIGHT REGIONS 177 

scanned. For there turns out to be something 
at these junctions. This something shows itself 
as a round or oval spot. To such spot, planted 
there in the midst of the desert at the junction, 
do the neighboring canals converge. 

Dotted all over the reddish-ochre ground of 
the desert stretches of the planet, the so-called 
continents of Mars, are an innumerable number 
of dark circular or oval spots. They appear, 
furthermore, always in intimate association with 
the canals. They constitute so many hubs to 
which the canals make spokes. These spots, 
together with the canals that lead to them, are 
the only markings to be seen anywhere on the 
continental regions. Otherwise the great red- 
dish-ochre areas are absolutely bare ; of that 
pale fire-opal hue which marks our own deserts 
seen from far. 

That these two things, — straight lines and 
roundish spots, — should, with our present tele- 
scopic means, be the sole markings to appear 
on the vast desert regions of the planet is sug- 
gestive in itself. 

Another significant fact as to the character 
of either marking is the manifest association of 
the two. In spite of the great number of the 
spots, not one of them stands isolate. There is 
not a single instance of a spot that is not con- 
nected by a canal to the rest of the dark areas. 
This remarkable inability to stand alone shows 



178 MARS 

that the spots and the canals are not unrelated 
phenomena, for were there no tie between them 
they must occasionally exist apart. 

Nor is this all. There is, apparently, no spot 
that is not joined to the rest of the system, not 
only by a canal, but by more than one; for 
though some spots, such as the Fountain of 
Youth, have appeared at first to be provided 
with but a single canal connection, later ob- 
servation has revealed concurrence in the case. 
The spots are, therefore, not only part and par- 
cel of the canal system, but terminal phenomena 
of the same. 

In the first place, as I have said, there ap- 
pears to be no spot that has not two or more 
canals running to it -, in the second place, I find, 
reversely, that apparently no canal junction is 
without its spot. Such association is a most 
tell-tale circumstance. I believe the rule to 
have no exception. The more prominent junc- 
tions all show spots ; and with regard to the 
less conspicuous ones, it is to be remembered 
that, as the canals are more easy to make out 
than the spots, the relative invisibility of the 
latter is to be expected. From which it would 
seem that the spots are fundamental features of 
the junctions, and that for a junction to be spot- 
less is, from its very nature, an impossibility. 

Next to their regularity of position is to be 
remarked their regularity of form. Their typi- 



SPOTS IN THE LIGHT REGIONS 179 

cal shape seems to be circular ; for the better 
the atmosphere, the rounder they look. Under 
poor seeing they show as irregular patches 
smooching the disk, much as the canals them- 
selves show as streaks ; the spots differing from 
the canals in being thicker and not so long. As 
the seeing improves, the patches differentiate 
themselves into round dots and connecting lines. 
Such is the shape of the spots associated with 
single canals ; that is, canals not double. In the 
case of the double canals, the spots look like 
rectangles with the corners rounded off. One 
of the most striking of all of them is the Tri- 
vium Charontis, which is nearly square. 

Now it will be noticed that these shapes are 
as imnatural as they are definite, and that they 
all agree in one peculiarity : they are all convex, 
not concave, to the entering canals. They are 
not, therefore, mere enlargements of the canals, 
due to natural causes ; for, were the spots en- 
largements of the canals, at their crossing-points 
they should be more or less star-shaped, or con- 
cave to the canals, whereas they are round, or 
roundish rectangles, — that is, convex to the 
same. Such convexity negatives, at the outset, 
their being purely natural outgrowths of the 
canals. 

The majority of the spots are from 120 to 
150 miles in diameter; thus presenting a cer- 
tain uniformity in size as well as in shape. 



180 MARS 

There are also smaller ones, not more than 75 
miles across, or less. 

To the spot category belong, apparently, all 
the markings other than canals to be seen any- 
where on the continental deserts of the planet, 
from the great Lake of the Sun, which is 540 
miles long by 300 miles broad, to the tiny 
Fountain of Youth, which is barely distinguish- 
able as a dot. That all are fundamentally of a 
kind is hinted at by their shape and emphasized 
by their character, a point to which we shall 
now come. 

To this end, we will start with an account of 
where and how they begin to show; for, like 
the canals, they are not permanent markings, 
but temporary phenomena. It is in the region 
about the Solis Lacus that they appear first. 
The Solis Lacus, or Lake of the Sun, is perhaps 
the most striking marking on Mars. It is an 
oval spot in lat. 28° S., with its greater diameter 
nearly perpendicular to the meridians, and en- 
circled by an elliptical ring of reddish-ochre 
land, which in turn is bordered on the south by 
the blue-green regions of the south temperate 
zone. The whole configuration is such as to 
simulate a gigantic eye which uncannily turns 
round upon one as the planet slowly revolves. 
It is so conspicuous a feature of the disk that it 
has been recognized for a great many years. 
The resemblance to an eye is further borne out 



SPOTS IN THE LIGHT REGIONS 181 

by a cordon of canals that surround it on the 
north. Upon this cordon, composed of the 
Araxes, the Daemon, and the Agathodaamon, 
are beaded a number of spots, two of them, the 
Phoenix and the Tithonius lakes, being conspic- 
uously prominent. Closer scrutiny reveals sev- 
eral more of the same sort, only smaller. These 
are all interconnected by a network of canals. 
Now just as it is in this region that the canals 
first show, so likewise is it here that the spots 
first make their appearance. 

Although it was here that at this last opposi- 
tion the spots were first seen, it was not here 
that their character and purpose became appar- 
ent. It was not until later in the season, when 
the Eumenides-Orcus began to give evidence of 
being yet more peculiarly beaded, that the true 
nature of the spots suggested itself to me. 

The Eumenides-Orcus is a very long and im- 
portant canal, connecting the Phoenix Lake 
with the Trivium Charontis. It is so long — 
3,540 miles from one end of it to the other — 
that, although it starts in lat. 16° N. and ends 
in lat. 12° S., it belts the disk not many degrees 
inclined to the equator. For a great distance it 
runs parallel to the northern coast of the Sea 
of the Sirens. From this coast several canals 
strike down to it ; some stopping at it, others 
continuing on down the disk. Especially is the 
western end of the sea, called the Gulf of the 



182 MARS 

Titans, a point of departure for canals ; no less 
than six of them, and doubtless more, leaving 
the gulf in variously radiating directions. At 
the place where these canals severally cross the 
Eumenides-Orcus, I began in November to see 
spots. I also saw others along the Pyriphlege- 
thon, an important canal leading in a more 
northerly direction from the Phoenix Lake ; 
along the Gigas, a great canal running from 
the Gulf of the Titans all the way to the Lake 
of the Moon ; and along other canals in the 
same region. I then noticed that the spots to 
the north of the SoHs Lacus region had dark- 
ened, since August, relatively to the more 
southern ones. In short, I became aware both 
of a great increase in the number of spots, and 
of an increase in tint in the spots previously 
seen. 

It was apparent that the spots were part and 
parcel of the canal system, and that in the 
matter of varying visibility they took after 
the canals, — chronologically, very closely after 
them; for a comparison of the two leads me 
to believe that the spots make their appearance 
subsequent, although but little subsequent, to 
the canals which conduct to them. 

Furthermore, the spots, like the canals, grow 
in conspicuousness with time. Now, when we 
consider that nothing, practically, has changed 
between us and them in the interval ; that 



SPOTS IN THE LIGHT REGIONS 183 

there has been no symptom of cloud or other 
obscuration, before or after, over the place 
where they eventually appear, — we are led to 
the conclusion that, like the canals, they grow. 

Indeed, in the history of their development 
the two features seem quite similar. Both 
grow, and both follow the same order and 
method in their growth. Both are affected by 
one progressive change that sweeps over the 
face of the planet from the pole to the equator, 
and then from the equator toward the other 
pole. In the case of the southern hemisphere, 
it is, as we have just seen, the most southern 
spots, like the most southern canals, that ap- 
pear first after the melting of the polar snows. 
Then gradually others begin to show farther 
and farther north. The quickening of the 
spots, like the quickening of the canals, is a 
seasonal affair. But there is more in it than 
this. It takes place in a manner to imply that 
something more immediate than the change in 
the seasons is concerned in it -, immediate not 
in time, but in relation to the result. A com- 
parison of the behavior of three spots — the 
Phoenix Lake, Ceraunius, the spot at the junc- 
tion of the Iris and the Gigas, and the Cyane 
Tons, a spot where the Steropes, a newly found 
canal, and the Nilus meet — will serve to point 
out what this something is. The Phoenix Lake 
lies in lat. 17° S., Ceraunius in lat. 12° N., and 



184 MARS 

the Cyane Fons in lat. 28° N. In August of 
last year, the first of these markings was very 
conspicuous, the second but moderately so, 
while the third was barely discernible. By 
November, the Phoenix Lake had become less 
salient, Ceraunius relatively more so, and the 
Cyane Fons nearly as evident as Ceraunius had 
formerly been. In the Martian calendar, the 
August observation corresponded to our 20th of 
June, the November one to our 1st of August. 
All three spots were practically within the 
equatorial regions. Now, on the Earth, no such 
marked progression in seasonal change occurs 
within the tropics. With us, it is to all intents 
and purposes equally green there the year 
through. On Mars it is not. Clearly, some 
more definite factor than the seasons enters 
into the matter upon our neighbor world. 

That this factor is water seems, from the be- 
havior of the blue-green areas generally, to be 
pretty certain. But just as the so-called seas 
are undoubtedly not seas, nor the canals water- 
ways, so the spots are not lakes. Their mode 
of growth, so far as it may be discerned, con- 
firms this conclusion. Apparently, it is not so 
much by an increase in size as by a deepening 
in tint that they gradually become recognizable. 
They start, it would seem, as big as they are 
to be, but faint in tone, premonitory shades 
of their future selves. They then proceed to 



SPOTS IN THE LIGHT REGIONS 185 

substantialize by darkening in tint throughout. 
N0W5 to deepen thus in color with one consent 
all over would be a peculiar thing for a lake 
to do. For had the lake appreciable depth to 
start with, it should always be visible ; and had 
it not, its bed would have to be phenomenally 
level to permit of its being all flooded at once. 
If, however, the spots be not bodies of water, 
but areas of verdure, their deepening in tint 
throughout is perfectly explicable, since the 
darkening would be the natural result of a 
simultaneous growth of vegetation. This in- 
ference is further borne out by the fact that 
to the spot class belong unquestionably those 
larger oval markings of which the Lake of the 
Sun is the most conspicuous example. For 
both are associated in precisely the same man- 
ner with the canal system. Each spot is a 
centre of canal connections in exactly the way 
in which the Solis Lacus or the Phoenix Lake 
itself is. But the light coming from the Solis 
Lacus and the Phoenix Lake showed, in Profes- 
sor W. H. Pickering's observations, no sign of 
polarization such as a sheet of water should 
show, and such as the polar sea actually did 
show. 

When we put all these phenomena together, 
— the presence of the spots at the junctions of 
the canals, their strangely systematic shapes, 
their seasonal darkening, and, last but not least, 



186 MARS 

the resemblance of the great continental regions 
of Mars to the deserts of the earth, — a solution 
of their character suggests itself at once ; to 
wit, that they are oases in the midst of that 
desert, and oases not wholly innocent of design ; 
for, in number, position, shape, and behavior, 
the oases turn out as typical and peculiar a 
feature of Mars as the canals themselves. 

Each phenomenon is highly suggestive con- 
sidered alone, but each acquires still greater 
significance from its association with the other -, 
for here in the oases we have an end and object 
for the existence of canals, and the most natural 
one in the world, namely, that the canals are 
constructed for the express purpose of fertiliz- 
ing the oases. Thus the mysterious rendezvous- 
ing of the canals at these special points is at 
once explicable. The canals rendezvous so en- 
tirely in defiance of the doctrine of chances 
because they were constructed to that end. 
They are not purely natural developments, but 
cases of assisted nature, just as they look to be 
at first sight. This, at least, is the only ex- 
planation that fully accounts for the facts. Of 
course all such evidence of design may be 
purely fortuitous, with about as much proba- 
bility, as it has happily been put, as that a 
chance collection of numbers should take the 
form of the multiplication table. 

In addition to this general dovetailing of 



SPOTS IN THE LIGHT REGIONS 187 

detail to one conclusion is to be noticed the 
strangely economic character of both the canals 
and the oases in the matter of form. That the 
lines should follow arcs of great circles, what- 
ever their direction, is as unnatural from a 
natural standpoint as it would be natural from 
an artificial one j for the arc of a great circle 
is the shortest distance from one point upon 
the surface of a sphere to another. It would, 
therefore, if topographically possible, be the 
course to take to conduct water, with the least 
expenditure of time or trouble, from the one 
to the other. 

The circular shape of the oases is as directly 
economic as is the straightness of the canals ; 
for the circle is the figure which incloses the 
maximum area for the minimum average dis- 
tance from its centre to any point situated 
within it. In consequence, if a certain amount 
of country were to be irrigated, intelligence 
would suggest the circular form in preference 
to all others, in order thus to cover the greatest 
space with the least labor. 

Following is the list of the oases so far dis- 
covered : — 



Acherusia Palus 
Aganippe Fons 
Alcyonia 
Ammonium 
Aponi Fons 



Aquae ApoUinares 
Aquae Calidae 
Arachoti Fons 
Arduenna 
Arethusa Fons 



188 



MARS 



Arsia Silva 
Arsine 
Augila 

Bandusiae Fons 
Biblis Fons 
Castalia Fons 
Ceraunius 
Clepsydra Fons 
Cyane Fons 
Ferentinae Lucus 
Fons Juventae 
Gallinaria Silva 
Hercynia Silva 
Hibe 

Hippocrene Fons 
Hipponitis Palus 
Hypelaeus 
Labeatis Lacus 
Lacus Ismenius 
Lacus Lunae 
Lacus Phoenicis 
Lerne 



Lucrinus Lacus 
Lucus Angitiae 
Lucus Feronia 
Lucus Maricae 
Maeisia Silva 
Mapharitis 
Mariotis 
Meroe 

Messeis Fons 
Nitriae 
Nodus Gordii 
Pallas Lacus 
Propontis 
Serapium 
Sirbonis Lacus 
Solis Fons 
Solis Lacus 
Tithonius Lacus 
Trinythios 
Trivium Charontis 
Utopia 



II. DOUBLE CANALS 

Even more markedly unnatural is another 
phenomenon of this most phenomenal system, 
of which almost every one has heard, and which 
almost nobody has seen, — the double canals. 

To see them, however, all that is needed is a 
sufficiently steady air, a sufficiently attentive 
observer, and the suitable season of the Mar- 
tian year. When these conditions are observed, 
the sight may be seen without difficulty, and is 
every whit as strange as Schiaparelli, who first 
saw it, has described it. 



DOUBLE CANALS 189 

So far as the observer is concerned, what 
occurs is this : Upon a part of the disk where 
up to that time a single canal has been visible, 
of a sudden, some night, in place of the single 
canals he perceives twin canals, — as like, in- 
deed, as twins, if not more so, similar both in 
character and in inclination, running side by 
side the whole length of the original canal, 
•usually for upwards of a thousand miles, of the 
same size throughout, and absolutely parallel to 
each other. The pair may best be likened to 
the twin rails of a railroad track. The regu- 
larity of the thing is startling. 

In good air the phenomenon is quite unmis- 
takable. The two lines are as distinct and as 
distinctly parallel as possible. No draughts- 
man could draw them better. They are tho- 
roughly Martian in their mathematical preci- 
sion. At the very first glance, they convey, 
like all the other details of the canal system, 
the appearance of artificiality. It may be well 
to state this here definitely, for the benefit of 
such as, without having seen the canals, in- 
dulge in criticism about them. No one who 
has seen the canals well — and the well is all- 
important for bringing out the characteristics 
that give the stamp of artificiality, the straight- 
ness and fineness of the lines — would ever 
have any doubt as to their seeming artificial, 
however he might choose to blind himseK to 



190 MARS 

the consequences. An element akin to the 
comic enters criticism based, not upon what the 
critics have seen, but upon what they have not. 
Books are reviewed without being read, to pre- 
vent prejudice ; but it is rash to carry the same 
admirable broad-mindedness into scientific sub- 
jects. 

In detail the doubles vary, chiefly, it would 
seem, in the distance the twin lines lie apart. 
In the widest I have seen, the Ganges, six de- 
grees separate the two ; in the narrowest, the 
Phison, four degrees and a quarter, — not a 
very great difference between the extremes. 
Four degrees and a quarter on Mars amount to 
156 miles ; six degrees, to 220. These, then, 
are the distances between the centres of the 
twin canals. Each canal seems a little less than 
a degree wide, or about 30 miles in the nar- 
rower instances ; in the broader, a little more 
than a degree, or about 45 miles. Between the 
two lines, in the cases where the gemination, 
as it is called, is complete, lies reddish-ochre 
ground similar to the rest of the surface of the 
bright regions. Deducting the two half- widths 
of the bordering canals, we have, therefore, from 
120 to 175 miles of clear country between the 
paralleling lines. 

This gemination of a canal is certainly a pass- 
ing strange phenomenon. Although, in steady 
air, the observation is not a difficult one, to see 



DOUBLE CANALS 191 

the region where it occurs minutely enough for 
a sufficient length of time to mark the details 
of the process is another matter. I shall here 
give what I have been able to gather at the 
last opposition, and shall hope to add to it at the 
next. One element of mystery may be elimi- 
nated at the outset. The process is not so sud- 
den as it seems. It is perceived of a sudden by 
the observer because of some specially favorable 
night. But it has been for some time develop- 
ing. So much is apparent from my observa- 
tions. Suggestions of duality occurred weeks 
before the thing stood definitely revealed. Fur- 
thermore, the gemination may lie concealed 
from the observer some time after it is quite 
complete, owing to lack of favorable atmospheric 
conditions. For it takes emphatically steady 
air to see it unmistakably. 

The next point is, that the phenomenon is 
individual to the particular canal. Each canal 
differs from its neighbor not only in the dis- 
tance the lines lie apart, but in the time at 
which duplication occurs. The event seems to 
depend both upon general seasonal laws govern- 
ing all the duplications, and upon causes intrin- 
sic to the canal itself. Within limits, each canal 
doubles at its own good time and after its own 
fashion. For example, although it seems to be 
a rule that north and south canals double before 
east and west ones, nevertheless, of two north 



192 MARS 

and soiith lines, one will double, the other will 
not, synchronously with a doubling running east 
and west ; the same is true of those running at 
any other inclination. 

Now this shows that the duplication is not an 
optical illusion at this end of the line ; for, by 
any double refraction here, all the lines running 
in the same direction over the disk should be 
similarly affected, which they are not. On 
the contrary, there will be, say, two cases of 
doubling in quite different directions coexistent 
with several single canals that run the same 
way. 

Nor is there any probability of its being a 
case of double refraction at the other end of the 
line, — that is, in the atmosphere of Mars ; for 
in that case it is hard to see why all the lines 
should not be affected, to say nothing of the 
fact that, to render such double refraction pos- 
sible, we must call upon a noumenon to help us 
out, as we know of no substance capable of the 
quality upon so huge a scale. Furthermore, 
what is cogent to the observer, though of no 
particular weight with his hearers, the pheno- 
menon has no look of double refraction. It 
looks to be, what it undoubtedly is, a double 
existence. 

Strengthening this conclusion is the mode of 
development of the doubling. This appears to 
take place in two ways, although it is possible 



DOUBLE CANALS 193 

that the two are but different instances of one 
and the same process. Of the first kind, during 
this last opposition, the Ganges was an example. 

The Ganges was in an interesting proto- 
plasmic condition during the whole of last sum- 
mer. About to multiply by fission, it was not 
at first evident how this would take place. 
Hints of gemination were visible when I first 
looked at it in August. It showed then as a 
very broad but not dark swath of dusky color, 
of nearly uniform width from one extremity to 
the other, with sides suggestively even through- 
out. It is probable that they were then, as 
afterward, parallel, and that the slight conver- 
gence apparent at the bottom was due simply 
to foreshortening. The swath ran thus north- 
northwest all the way from the Gulf of the 
Dawn to the Lacus Labeatis. By moments of 
better seeing, its two sides showed darker than 
its middle ; that is, it was already double in 
embryo, with a dusky middle-ground between 
the twin lines. 

In October the doubling had sensibly pro- 
gressed. The double visions were more fre- 
quent, and the ground between the twin lines 
had grown lighter. By November the doubling 
was unmistakable, and the mid-clarification had 
become nearly complete. It is to be remarked 
that the doubling did not involve the Fons 
Juventae and the canal leading to it, both of 



194 MARS 

which lay well to the right of the Ganges. The 
space included between the East and West 
Ganges was very wide, some six degrees. The 
canals themselves were, so far as could be seen, 
quite similar, and about a degree, or 37 miles, 
wide. Both started in the Gulf of the Dawn, 
and ran down to the lower Lake of the Moon, 
one entering each side of the lake or oasis. Two 
thirds of the way down, both similarly touched 
the sides of another oasis, an upper Lacus 
Lunae ; the other I have called the Lacus La- 
beatis. The length of each canal was 1200 miles. 

Except for fleeting suspicions of gemination, 
and for possible doublings like the parallelism of 
the two Hades, the next canal to show double 
was the Nectar, which was so seen by Mr. Doug- 
lass on October 4, and under still better seeing, 
a few minutes later, the doubling was detected 
by him extending straight across the Solis 
Lacus. In the Solis Lacus this was evidently 
a case of mid-clarification. What occurred in 
the Nectar seems more allied to the second class 
of manifestations, such as happened later with 
the Euphrates and the Phison. 

Glimpses of a dual state in these canals we 
caught during the summer and autumn, but it 
was not till the November presentation of the 
region that they came out unmistakably twinned. 
On the 18th of that month, just as the twilight 
was fading away, the air being very still and 



Plate XXIII 




PHISON AND EUPHRATES 

(Both double) 

November i8, 1894 



Lowell Observatory 
Flagstaff, A. T. 1894 



DOUBLE CANALS 195 

the definition exceptional, so soon as the sunset 
tremors subsided, the Euphrates and its neigh- 
bor the Phison I saw beautifully doubled, ex- 
actly like two great railroad tracks with bright 
ground between, each set extending down the 
disk for a distance of 1600 miles. 

After that evening, whenever the seeing was 
good enough, they continued to present the 
same appearance. Now, with them no process of 
midway clarification, such as had taken place in 
the Ganges, had previously made itself manifest. 
They had, indeed, not been very well defined 
before duplication occurred, but apparently suf- 
ficiently so not to hide such broadening had it 
taken place ; for, though the twin canals were 
not as far apart as the two Ganges, they were 
quite comparably distant, being, instead of six, 
about four and a quarter degrees from each 
other. Evidently, the process was, in the case 
of the Euphrates at least, under way in Octo- 
ber, and even earlier, but was not well seen 
because the twin canals were not yet dark 
enough. 

There seem, I may remark parenthetically, 
to be two other double canals in the region be- 
tween the Syrtis Major and the Sabaeus Sinus, 
one to the east of the Phison, and another 
between the Phison and the Euphrates, both 
debouching at the same points as the Phison 
and the Euphrates themselves. 



196 MARS 

On the 19th of November I suspected dupli- 
cation in the Typhon, another canal in the same 
region. It looked to be double, with dusky 
ground between. 

On the 21st I similarly suspected the Jamuna 
and the Dardanus. Both looked broad and 
dusky, with very ill-defined condensation at the 
sides. But the seeing was not good enough. 
On the 22d I brought my observations to an 
end, in consequence of having to return East. 

Exactly what takes place, therefore, in this 
curious process of doubling, I cannot pretend to 
say. It has been suggested that a progressive 
ripening of vegetation from the centre to the 
edges might cause a broad swath of green to be- 
come seemingly two. There are facts, however, 
that do not tally with this view. For example, 
the Ganges was always broad, but fainter, not 
narrower, earlier in the season. The Phison, on 
the other hand, went through no such process. 
Indeed, we are here very much in the dark, cer- 
tainly very far off from what does take place 
in Martian canal gemination. Perhaps we may 
learn considerably more about it at the next 
opposition. At this the tendril end of our 
knowledge of our neighbor we cannot expect 
hard wood. 

From these observations, and those of Schia- 
parelli, I feel, however, tolerably sure that the 
phenomenon is not only seasonal but vegetal. 



SPOTS IN THE DARK REGIONS 197 

Why it should take this form is one of the most 
pregnant problems about the planet. For it is 
the most artificial-looking phenomenon of an 
artificial-looking disk. 

III. SPOTS IN THE DARK REGIONS. 

To return now from these outposts of inves- 
tigation to our main subject-matter, and to an- 
other phenomenon of more recent discovery 
than the double canals, and yet more suggestive 
of interpretation. We have seen what shows at 
one end of the canals, their inner end ; namely, 
the oasis. But it seems that there is also some- 
thing exceptional at the other. At the mouth 
of each canal, at the edge of the so-called seas, 
appears a curious dark spot, of the form of a 
half -filled angle ; the sort of a mark with which 
one checks items on a list. Its form is singularly 
appropriate, according to mundane ideas, for it 
appears before the canal itself is visible, as if to 
mark the spot where the canal will eventually 
be. It lies in the so-called seas, and looks to be 
of the same color as they, but deeper in tint. 

All the canals that debouch into the dark 
regions are provided with these terminal tri- 
angles, except those that lead out of long estu- 
aries, like the Nilosyrtis, the Hiddekel, the 
Gihon, and so forth. The double canals are 
provided with twin triangles. That the trian- 
gular patches are phenomena connected with 



198 MARS 

the canals is evident from the fact that they 
never appear elsewhere. What exact purpose 
they serve is not so clear, but it would seem to 
be that of relay stations for the water before it 
enters the canals ; what we see, upon this sup- 
position, being, not the station or reservoir 
itself, but the specially fertile area round it. 

That, in addition to being in a way oases 
themselves, they serve some such purpose as the 
above, is further hinted at by two facts : first, 
that whereas the oases develop, apparently, after 
the canals leading to them, the triangular spots 
develop before the canals that lead out of them ; 
second, Mr. Douglass finds that it is in them 
that the canals in the dark regions terminate. 
They are the end of the one system at the same 
time that they are the beginning of the other. 
They would, therefore, seem to be way-stations 
of some sort on the road taken by the water 
from the polar cap to the equator. 

Paralleling in appearance the oases in the 
bright regions are round spots that occur at the 
junctions of the canals in the dark ones. Speak- 
ing figuratively, these are the heads of the nails 
in the coffin of the idea that the seas are seas ; 
since, if the blue-green color came from water, 
there could not be permanent darker dots upon 
it connected by equally dark streaks. Speaking 
unfiguratively, this shows that the whole system 
of canals and specially fertilized spots is not 



SPOTS IN THE DARK REGIONS 199 

confined to the deserts, but extends in a modi- 
fied form over the areas of more or less vegeta- 
tion. 

There are thus two kinds of spots in the 
dark regions : those on their borders, and those 
in their midst. The position of the former — 
on the edge of the great deserts — implies a 
difference in kind, further emphasized by their 
shape. Following is the list of both kinds de- 
tected at Flagstafi*: — 

SPOTS IN THE DARK REGIONS. 
Astrae Lacus. 
Benaciis Lacus. 
Cynia Lacus. 
Flevo Lacus. 
Hesperidum Lacus. 
Oxia Palus. 
Spot at the mouth of the Phison. 

" Euphrates. 

" Daix on the Mare Icarium. 

Spot at the mouth of the Daix on the Sabaeus Sinus. 
Spot on the Socratis Promontorium. 
Spot on the western side of the Socratis Promontorium. 

" Margaritifer Sinus. 

Spot at the mouth of the Jamuna on the Aurorae Sinus. 

" Ganges " 

" Hebe " 

" Agathodaemon " 

" Ambrosia on the Mare Australe. 

" Maeander on the Aonius Sinus. 

" Gorgon on the Mare Sirenum. 

" Erinaeus. 

" Titan on the Sinus Titanum. 



200 MARS 

Spot at the mouth of the Cophen on the Mare Cimmerium. 



a 


Laestiygon 




a 


it 


Nereides 




a 


a 


Cerberus 




a 


« 


Chretes 




6i 


ti 


Asopus on the 


Syrtis Major. 


u 


Arosis 


u 




a 


Typhon 


(( 




Spot south of the mouth of the Typhon 


(( 





We thus perceive that the blue-green areas 
are subjected to the same engineering system 
as the bright ones. In short, no part of the 
planet is allowed to escape from the all-pervasive 
trigonometric spirit. If this be Nature's doing, 
she certainly here runs her mathematics into 
the ground. 



VI 

CONCLUSION 

To review, now, the chain of reasoning by 
which we have been led to regard it probable 
that upon the surface of Mars we see the effects 
of local intelligence. We find, in the first place, 
that the broad physical conditions of the planet 
are not antagonistic to some form of life ; sec- 
ondly, that there is an apparent dearth of water 
upon the planet's surface, and therefore, if be- 
ings of sufficient intelligence inhabited it, they 
would have to resort to irrigation to support 
life ; thirdly, that there turns out to be a net- 
work of markings covering the disk precisely 
counterparting what a system of irrigation 
would look like ; and, lastly, that there is a set 
of spots placed where we should expect to find 
the lands thus artificially fertilized, and behav- 
ing as such constructed oases should. All this, 
of course, may be a set of coincidences, signify- 
ing nothing ; but the probability points the 
other way. As to details of explanation, any 
we may adopt will undoubtedly be found, on 
closer acquaintance, to vary from the actual 
Martian state of things; for any Martian life 
must differ markedly from our own. 



202 MAES 

The fundamental fact in the matter is the 
dearth of water. If we keep this in mind, we 
shall see that many of the objections that spon- 
taneously arise answer themselves. The sup- 
posed herculean task of constructing such canals 
disappears at once ; for, if the canals be dug for 
irrigation purposes, it is evident that what we 
see, and call by ellipsis the canal, is not really 
the canal at all, but the strip of fertilized land 
bordering it, — the thread of water in the midst 
of it, the canal itself, being far too small to be 
perceptible. In the case of an irrigation canal 
seen at a distance, it is always the strip of ver- 
dure, not the canal, that is visible, as we see in 
looking from afar upon irrigated country on the 
Earth. 

We may, perhaps, in conclusion, consider for 
a moment how different in its details existence 
on Mars must be from existence on the Earth. 
One point out of many bearing on the subject, 
the simplest and most certain of all, is the effect 
of mere size of habitat upon the size of the 
inhabitant ; for geometrical conditions alone are 
most potent factors in the problem of life. 
Volume and mass determine the force of grav- 
ity upon the surface of a planet, and this is 
more far-reaching in its effects than might at 
first be thought. Gravity on the surface of 
Mars is only a little more than one third what 
it is on the surface of the Earth. This would 



CONCLUSION 203 

work in two ways to very different conditions 
of existence from those to which we are accus- 
tomed. To begin with, three times as much 
work, as for example, in digging a canal, could 
be done by the same expenditure of muscular 
force. If we were transported to Mars, we 
should be pleasingly surprised to find all our 
manual labor suddenly lightened threefold. 
But, indirectly, there might result a yet 
greater gain to our capabilities ; for if Nature 
chose she could afford there to build her in- 
habitants on three times the scale she does on 
Earth without their ever finding it out except 
by interplanetary comparison. Let us see how. 

As we all know, a large man is more un- 
wieldy than a small one. An elephant refuses 
to hop like a flea ; not because he considers the 
act undignified, but simply because he cannot 
bring it about. If we could, we should all 
jump straight across the street, instead of pain- 
fully paddling through the mud. Our inability 
to do so depends upon the size of the Earth, not 
upon what it at first seems to depend on, the 
size of the street. 

To see this, let us consider the very simplest 
case, that of standing erect. To this every-day 
feat opposes itself the weight of the body 
simply, a thing of three dimensions, height, 
breadth, and thickness, while the ability to 
accomplish it resides in the cross-section of the 



204 MARS 

muscles of the knee, a thing of only two dimen- 
sions, breadth and thickness. Consequently, a 
person half as large again as another has about 
twice the supporting capacity of that other, but 
about three times as much to support. Standing 
therefore tires him out more quickly. If his 
size were to go on increasing, he would at last 
reach a stature at which he would no longer be 
able to stand at all, but would have to lie 
down. You shall see the same effect in quite 
inanimate objects. Take two cylinders of paraf- 
fine wax, one made into an ordinary candle, the 
other into a gigantic facsimile of one, and then 
stand both upon their bases. To the small one 
nothing happens. The big one, however, 
begins to settle, the base actually made viscous 
by the pressure of the weight above. 

Now apply this principle to a possible inhabit- 
ant of Mars, and suppose him to be constructed 
three times as large as a human being in every 
dimension. If he were on Earth, he would 
weigh twenty-seven times as much, but on the 
surface of Mars, since gravity there is only 
about one third of what it is here, he would 
weigh but nine times as much. The cross-sec- 
tion of his muscles would be nine times as 
great. Therefore the ratio of his supporting 
power to the weight he must support would be 
the same as ours. Consequently, he would be 
able to stand with as little fatigue as we. Now 



CONCLUSION 205 

consider the work he might be able to do. His 
muscles^ having length, breadth, and thickness, 
would all be twenty-seven times as effective as 
ours. He would prove twenty-seven times as 
strong as we, and could accomplish twenty- 
seven times as much. But he would further 
work upon what required, owing to decreased 
gravity, but one third the effort to overcome. 
His effective force, therefore, would be eighty- 
one times as great as man's, whether in digging 
canals or in other bodily occupation. As grav- 
ity on the surface of Mars is really a little more 
than one third that at the surface of the Earth, 
the true ratio is not eighty-one, but about fifty ; 
that is, a Martian would be, physically, fifty- 
fold more efficient than man. 

As the reader will observe, there is nothing 
problematical about this deduction whatever. 
It expresses an abstract ratio of physical capa- 
bilities which must exist between the two 
planets, quite irrespective of whether there be 
denizens on either, or how other conditions 
may further affect their forms. As the reader 
must also note, the deduction refers to the pos- 
sibility, not to the probability, of such giants ; 
the calculation being introduced simply to show 
how different from us any Martians may be, not 
how different they are. 

It must also be remembered that the ques- 
tion of their size has nothing to do with the 



206 MAKS 

question of their existence. The arguments for 
their presence are quite apart from any consid- 
eration of avoirdupois. No Herculean labors 
need to be accounted for ; and, if they did, brain 
is far more potent to the task than brawn. 

Something more we may deduce about the 
characteristics of possible Martians, dependent 
upon Mars itself, a result of the age of the 
world they would live in. 

A planet may in a very real sense be said to 
have life of its own, of which what we call life 
may or may not be a subsequent detail. It is 
born, has its fiery youth, sobers into middle 
age, and just before this happens brings forth, 
if it be going to do so at all, the creatures on 
its surface which are, in a sense, its offspring. 
The speed with which it runs through its 
gamut of change prior to production depends 
upon its size ; for the smaller the body the 
quicker it cools, and with it loss of heat means 
beginning of life for its offspring. It cools 
quicker because, as we saw in a previous chapter, 
it has relatively less inside for its outside, and it 
is through its outside that its inside cools. After 
it has thus become capable of bearing life, the 
Sun quickens that life and supports it for we 
know not how long. But its duration is meas- 
ured at the most by the Sun's life. Now, 
inasmuch as time and space are not, as some 
philosophers have from their too mundane stand- 



^^ 



CONCLUSION 207 

point supposed, forms of our intellectj but 
essential attributes of the universe, the time 
taken by any process affects the character of 
the process itself, as does also the size of the 
body undergoing it. The changes brought 
about in a large planet by its cooling are not, 
therefore, the same as those brought about in a 
small one. Physically, chemically, and, to our 
present end, organically, the two results are 
quite diverse. So different, indeed, are they 
that unless the planet have at least a certain 
size it will never produce what we call life, 
meaning our particular chain of changes or 
closely allied forms of it, at all. As we saw in 
the case of atmosphere, it will lack even the 
premise to such conclusion. 

Whatever the particular planet's line of devel- 
opment, however, in its own line, it proceeds to 
greater and greater degrees of evolution, till 
the process stops, dependent, probably, upon the 
Sun. The point of development attained is, as 
regards its capabilities, measured by the planet's 
own age, since the one follows upon the other. 

Now, in the special case of Mars, we have be- 
fore us the spectacle of a world relatively well 
on in years, a world much older than the Earth. 
To so much about his age Mars bears evidence 
on his face. He shows unmistakable signs of 
being old. Advancing planetary years have left 
their mark legible there. His continents are all 



208 MAES 

smoothed down ; his oceans have all dried up. 
Teres atque rotundus, he is a steady-going body 
now. If once he had a chaotic youth, it has 
long since passed away. Although called after 
the most turbulent of the gods, he is at the 
present time, whatever he may have been once, 
one of the most peaceable of the heavenly host. 
His name is a sad misnomer; indeed, the an- 
cients seem to have been singularly unfortunate 
in their choice of planetary cognomens. With 
Mars so peaceful, Jupiter so young, and Venus 
bashfully draped in cloud, the planet's names 
accord but ill with their temperaments. 

Mars being thus old himself, we know that 
evolution on his surface must be similarly ad- 
vanced. This only informs us of its condition 
relative to the planet's capabilities. Of its 
actual state our data are not definite enough to 
furnish much deduction. But from the fact that 
our own development has been comparatively 
a recent thing, and that a long time would be 
needed to bring even Mars to his present geolo- 
gical condition, we may judge any life he may 
support to be not only relatively, but really 
older than our own. 

From the little we can see, such appears to 
be the case. The evidence of handicraft, if such 
it be, points to a highly intelligent mind behind 
it. Irrigation, unscientifically conducted, would 
not give us such truly wonderful mathematical 



CONCLUSION 209 

fitness in the several parts to the whole as we 
there behold. A mind of no mean order would 
seem to have presided over the system we see, 
— a mind certainly of considerably more com- 
prehensiveness than that which presides over 
the various departments of our own public 
works. Party politics, at all events, have had 
no part in them ; for the system is planet wide. 
Quite possibly, such Martian folk are possessed 
of inventions of which we have not dreamed, 
and with them electrophones and kinetoscopes 
are things of a bygone past, preserved with 
veneration in museums as relics of the clumsy 
contrivances of the simple childhood of the race. 
Certainly what we see hints at the existence of 
beings who are in advance of, not behind us, in 
the journey of life. 

Startling as the outcome of these observations 
may appear at first, in truth there is nothing 
startling about it whatever. Such possibility 
has been quite on the cards ever since the ex- 
istence of Mars itself was recognized by the 
Chaldean shepherds, or whoever the' still more 
primeval astronomers may have been. Its 
strangeness is a purely subjective phenomenon, 
arising from the instinctive reluctance of man 
to admit the possibility of peers. Such would 
be comic were it not the inevitable consequence 
of the constitution of the universe. To be shy 
of anything resembling himself is part and par- 



210 MARS 

eel of man's own individuality. Like the savage 
who fears nothing so much as a strange man, 
like Crusoe who grows pale at the sight of foot- 
prints not his own, the civilized thinker instinc- 
tively turns from the thought of mind other 
than the one he himself knows. To admit into 
his conception of the cosmos other finite minds 
as factors has in it something of the weird. 
Any hypothesis to explain the facts, no matter 
how improbable or even palpably absurd it be, 
is better than this. Snow-caps of solid carbonic 
acid gas, a planet cracked in a positively mono- 
maniacal manner, meteors ploughing tracks 
across its surface with such mathematical pre- 
cision that they must have been educated to 
the performance, and so forth and so on, in 
hypotheses each more astounding than its pre- 
decessor, commend themselves to man, if only 
by such means he may escape the admission of 
anything approaching his kind. Surely all this 
is puerile, and should as speedily as possible be 
outgrown. It is simply an instinct like any 
other, the projection of the instinct of self-pre- 
servation. We ought, therefore, to rise above 
it, and, where probability points to other things, 
boldly accept the fact provisionally, as we should 
the presence of oxygen, or iron, or anything 
else. Let us not cheat ourselves with words. 
Conservatism sounds finely, and covers any 
amount of ignorance and fear. 



CONCLUSION 211 

We must be just as careful not to run to the 
other extreme, and draw deductions of purely 
local outgrowth. To talk of Martian beings is 
not to mean Martian men. Just as the proba- 
bilities point to the one, so do they point away 
from the other. Even on this Earth man is of 
the nature of an accident. He is the survival 
of by no means the highest physical organism. 
He is not even a high form of mammal. Mind 
has been his making. For aught we can see, 
some lizard or batrachian might just as well 
have popped into his place early in the race, 
and been now the dominant creature of this 
Earth. Under different physical conditions, he 
would have been certain to do so. Amid the 
surroundings that exist on Mars, surroundings 
so different from our own, we may be practi- 
cally sure other organisms have been evolved 
of which we have no cognizance. What man- 
ner of beings they may be we lack the data 
even to conceive. 

For answers to such problems we must look 
to th© future. That Mars seems to be inhabited 
is not the last, but the first word on the sub- 
ject. More important than the mere fact of 
the existence of living beings there, is the 
question of what they may be like. Whether 
we ourselves shall live to learn this cannot, of 
course, be foretold. One thing, however, we 
can do, and that speedily : look at things from a 
standpoint raised above our local point of view ; 



212 MARS 

free our minds at least from the shackles that 
of necessity tether our bodies; recognize the 
possibility of others in the same light that 
we do the certainty of ourselves. That we are 
the sum and substance of the capabilities of the 
cosmos is something so preposterous as to be 
exquisitely comic. We pride ourselves upon 
being men of the worlds forgetting that this is 
but objectionable singularity, unless we are, in 
some wise, men of more worlds than one. For, 
after all, we are but a link in a chain. Man is 
merely this, earth's highest production up to 
date. That he in any sense gauges the possi- 
bilities of the universe is humorous. He does 
not, as we can easily foresee, even gauge those 
of this planet. He has been steadily bettering 
from an immemorial past, and will apparently 
continue to improve through an incalcul^.ble 
future. Still less does he gauge the universe 
about him. He merely typifies in an imperfect 
way what is going on elsewhere, and what, to a 
mathematical certainty, is in some corners of 
the cosmos indefinitely excelled. 

If astronomy teaches anything, it teaches 
that man is but a detail in the evolution of the 
universe, and that resemblant though diverse 
details are inevitably to be expected in the host 
of orbs around him. He learns that, though he 
will probably never find his double anywhere, 
he is destined to discover any number of cousins 
scattered through space. 



APPENDIX 

Note I 
The critical velocity at the surfaces of the planets is found 
as follows : — 

Using the usual symbols we have : 
fdt = dv 
.'. fds = vdv. 

And as/ = ^^, since the force tends to decrease the coordi- 
nates, this becomes ^ =: vdv. 

Integrating : 
m 
s 
m m 

Si $2 

Hence, since at infinity the velocity is 0, the equation for a 
fall to a planet's surface from infinity is 

r being the radius of the planet and v the velocity acquired at 
its surface from a fall from infinity, which is the same as the 
velocity needed for projection from its surface to infinity. 

To find m we have in the case of the Earth g=32 ft. a second 
at its surface ; this gives us m in terms of g, that is,/. For the 
other planets we need only to introduce their masses and radii in 
terms of those of the Earth and then multiply the value for the 
Earth by the square root of the ratio. 

The result is that we find the critical velocity for the several 
planets and for the Sun to be as follows : — 

Mercury 2.2 miles a second (probable value). 



=r ^ v"^ -\- c, oi which the definite integral from Si to s^ is 

V? - i vi . 



Venus 


6.6 


Earth 


6.9 


Moon 


1.5 



214 





APPENDIX 






Mars 


3.1 miles 


a second. 




Jupiter 


37. 


« 


(( 


tt 


(mean value). 


Saturn 


22. 


(( 


u 


a 


(( (( 


Uranus 


13. 


ii 


a 


u 


il u 


Neptune 


14. 


a 


<c 


a 


11 (( 


Sun 


382. 


a 


(( 


« 





While the probable maximum speed of the molecules of some 
of the commoner gases at 0° Cent, are as follows : — 
Hydrogen 7.4 miles a second. 

Water vapor 2.5 " " " 

Nitrogen 2.0 « « « 

Oxygen 1.8 « " « 

Carbonic dioxide 1.6 « « « 



Note II 



The change in the apparent size of the equatorial diam- 
eter as compared with the polar one as the phase increased, 
suggesting the unconscious measurement of a twilight upon 
the planet, becomes still more striking when, in addition to 
the October-November measures mentioned in the text, the 
measures from July to October are considered in connection 
with them. Tabulated chronologically, the whole are as fol- 
lows : — 

MEANS 

Polar Diameters 

Cor. for Cor. for 

ref. irr. vmy, Angle ref. irr. 

tilt and giL" " of tilt and 

phase phase phase 

Irr. O'MO Irr. 0'M5 

July (6 to 22 inc.) 9.976 0'M3 0° 9.933 

Aug. (11 to 21 inc.) 9.362 0''.04 0° 9.325 

Sept. (20 to Oct. 5 inc.) 9.401 0''.012 0° 9.355 

Oct. (12 & 24 to 30 inc.) 9.375 0''.028 1° 9.336 

Oct. (15 to 23 inc.) 9.379 0".011 2°.5 9.339 

Oct. (12 & 24 to 30 inc.) 9.375 0".028 1° 9.336 

Nov. (2 to 21 inc.) 9.390 0''.012 4° 9.350 



APPENDIX 215 



Equatorial Diameters 
July (6 to 22 inc.) 9.691 > O'Ml ) 46°.5 9.672 



Aug. (11 to 21 inc.) 9.666 > "•""" 0'M5 > " *"" 41° 9.645 

Sept.(20 to Oct. 5) 9.523 0''.010 20°.5 9.490 

Oct. (12 & 24 to 30 inc.) 9.457 0''.016 7° 9.417 

Oct. (15 to 23 inc.) 9.429 O^'.OIO 1° 9.385 

Oct. (12 & 24 to 30 inc.) 9.457 0".016 7° 9.417 

Nov. (2 to 21 inc.) 9.545 0'^015 19° 9.514 

It will be seen that, except for the July value, the size of 
the polar diameter comes out essentially the same through- 
out. Now, during July the polar cap was very large, and 
covered the southern part of the disk at the point where the 
polar diameter was measured. As it was much brighter 
than the rest of the disk, its irradiation must have been cor- 
respondingly great, and this would have had the effect of 
increasing the apparent length of the polar diameter beyond 
its true value. 

The equatorial measures, on the other hand, show a sys- 
tematic increase as the phase increased ; and they do this 
on both sides of opposition. The increase, it will be noticed, 
is much greater than the probable errors of observation. 



Note III 



As the statement has been widely circulated that recent 
spectroscopic observations negative an atmosphere on Mars, 
it may be well to mention in a note that the observations in 
question neither affirm nor deny its presence, as their self- 
disclosed measure of precision, i of an atmosphere, proves 
them incapable of it. They simply concur in showing that 
atmosphere to be thin. As a matter of fact, if spectroscopic 
observations did deny the existence of an atmosphere on 
Mars, such assertion would be fatal, not to the atmosphere, 
but to the observer or his instrument, as the existence of an 
atmosphere is demonstrated by the fundamental laws of 



216 APPENDIX 

physics, inasmuch as no change could take place on the plan- 
et's surface without it, and that changes do take place is 
undeniable. (See page 31 et seq.) 



Note IV 



Mars has two satellites, discovered by Hall in 1877, and 
known as Deimos (Dread) and Phobos (Fear), named in 
keeping with the God of War. 

Deimos, at a distance of 14,600 miles from the planet's 
centre, makes his circuit in 30 hours and 18 minutes ; Phobos, 
at a distance of 5,800, in 7 hours and 39 minutes. As Mars 
himself rotates in 24 hours and 39 minutes, Phobos goes 
round the planet faster than the planet turns upon itself, 
and, in consequence, would appear to any observers on the 
planet's surface to break the otherwise universal conformity 
of stellar motions by rising in the west and setting in the 
east. Deimos, too, is just as unconventional in its way, 
for it remains for two days at a time about the horizon. 
Furthermore, with each, owing to its nearness to the planet, 
its distance from any place on the surface varies at different 
times, and with its distance varies its apparent size in a some- 
what startling manner. 

As for themselves, they are very minute bodies, though 
not so difficult to see as is commonly stated. In the clear 
air of Arizona, both were conspicuous objects. They appear 
as stars of about the 12th and 10th magnitudes respectively ; 
Phobos being much larger, relatively to Deimos, than its 
hitherto accepted value would indicate. Observations at 
Flagstaff by both Mr. Douglass and by me agree in making 
its relative brilliancy such as to give it a diameter about 3.6 
times that of Deimos. It is not usually so conspicuous as 
Deimos, in spite of its size, because of its proximity to the 
planet, and the consequent much greater illumination of 
the field upon which it is seen. Considering their most 
probable albedoes as somewhat less than that of our moon, 



APPENDIX 217 

we find from their stellar magnitudes, taking the stellar 
magnitude found for Deimos by Pickering in 1877 as basis, 
their diameters to be, — 

Deimos, about 10 miles ; 
Phobos, about 36 miles. 
Phobos would thus, at its closest approach to the surface of 
the planet, that is, when it was in the zenith, just show a 
disk like the Moon. Otherwise both satellites would appear 
as stars. 

Neither satellite shares the red tint of the planet. 



Note V. 



As the means employed in any astronomical observation 
are of interest, I may add that the telescope used in these 
researches was an 18-inch refractor, made by Brashear, of 
Alleghany, Pa., the largest he has yet made. The powers 
used varied from 320 to 1305 diameters, the usual ones be- 
ing, for visual purposes, 440 and 617, and, for micrometric 
measurements, 862. There is, not unnaturally, much mis- 
conception prevalent as to the magnification possible in a 
telescope. The highest powers of a glass can never be used 
on planetary detail, as the tremors of the air blur the image. 
Thus we come back again to the question of atmosphere, 
which is indeed the crux ohservationis. With regard to 
work on the planets, the important point about an observa- 
tory is not so much what is its lens as what is its location. 



? 



■C) \ 6^ 



Pla- 




Noi 



m:ap oij 

on Mercator' 



XXIV 



200 '.'10 TIO 2:;0 210 250 2(50 270 2o0 200 .'iOO 310 :J20 330 310 350 3C0 

— i \ \ } ] 1 ] ; ] ] 1 c 1 1 1 \ r- 




P.L. 



' MARS 
s Projecfcion 



Lowell Observatory 
Flagstaff, A. T. 1895 



INDEX OF NAMES ON THE MAP OF MAES 

ARRANGED ALPHABETICALLY 

REGIONS 



No. 



Name 



No. 



Name 



100 Aonius Sinus 

7 Argyre 
168 Atlantis 
15 Aurorae Sinus 
287 Ausonia 

4 Deucalionis Regie 
268 Edom Promontorium 
194 Elysium 

1 Fastigium Aryn 
229 Hadriaticum Mare 
240 Hammonis Cornu 
275 Hellas 
211 Hesperia 
205 Isidis Regie 



236 Japygia 
225 Leniuria 
207 Libya 
176 Mare Chrouium 
165 Mare Cimmerium 
285 Mare Erythraeum 
283 Mare Icarium 
173 Mare Sirenum 
210 Mare Tyrrhenum 

20 Margaritifer Sinus 
103 Memnonia 

6 Noachis 
277 Oenotria 

88 Ogygis Regie 



No. Name 
286 Ophir 
9 Protei Regio 
5 Pyrrhae Regio 
3 Sabaeus Sinus 
2 Socratis Promonto- 
rium 
233 Syrtis Major 
237 Solis Promontorium 
209 Syrtis Parva 
27 Tempe 
92 Tliyle I. 
177 Thyle II. 
267 Xisuthri 



No. Name 
271 Acalandrus 

84 Acampsis 

10 Acesines 
119 Achana 
222 Achates 
199 Achelous 
284 Acheron 

90 Acis 
238 Aeolus 

76 Aesis 
192 Aethiops 

43 Agathodaemon 
273 Alpheus 

87 Ambrosia 

203 Amenthes 
12 Amphrysus 
54 Amystis 

61 Anapus 

161 Antaeus 

242 Anubis 
79 Araxes 

144 Arges 

244 Arosis 
250 Arsanias 

62 Artanes 

243 Asopus 

245 Astaboras 

204 Astapus 
156 Atax 
224 Athesis 
163 Avernus 

73 Avus 

162 Axius 
148 Axon 

57 Bactrus 



CANALS 



Name 



No. 
37 Baetis 
86 Bathys 

159 Bautis 
143 Belus 
198 Boreas 
201 Boreosyrtis 
129 Brontes 

16 Caicus 
189 Cambyses 

22 Cantabras 
232 Carpis 
239 Casuentus 

55 Catarrhactes 

94 Cayster 
221 Centrites 
218 Cephissus 
186 Cerberus 

14 Oestrus 
182 Chaboras 
184 Chretes 

42 Chrysas 

49 Chrysorrhoas 
212 Cinyphus 

47 Clitumnus 

64 Clodianus 

160 Cophen 
44 Coprates 
40 Corax 

164 Cyaneus 

91 Cyrus 

77 Daemon 
260 Daix 
258 Daradax 

26 Dardanus 

19 Dargamanes 



No. Name 

264 Deuteronilus 

172 Digentia 

235 Dosaron 
93 Drahonus 

107 Elison 
74 Eosphorus 
18 Erannoboas 

150 Erebus 

141 Erinaeus 
226 Erymanthus 

104 Erynnis 
256 Eulaeus 
114 Eumenides 
193 Eunostos 
253 Euphrates 
140 Eurymedon 
213 Eurypus 

142 ETenus 
67 Fortunae 

179 Gaesus 

215 Galaesus 

197 Galaxias 
36 Ganges 
48 Ganymede 
13 Garrhuenus 

122 Gigas 

266 Gihon 
63 Glaucus 

105 Gorgon 
145 Gyes 
153 Hades 

70 Halys 
170 Harpasus 

38 Hebe 
181 Helisson 



220 INDEX OF NAMES ON THE MAP OF MARS 



No. 



Name 



No. 



Name 



No. 



Name 



171 Heratemis 

101 Herculis Columnae 
261 Hiddekel 

17 Hipparis 
231 Hippus 
234 Hyctanis 

82 Hydaspes 

34 Hydraotes 
11 Hydriacus 

227 Hylias 
272 Hyllus 
31 Hyphasis 

35 Hypsas 

102 Hyscus 
30 Indus 
68 Iris 

95 Isis 

28 Jamuna 

80 Jaxartes 
257 Labotas 
155 Laestrygon 
166 Leontes 
202 Lethes 

139 Liris 

81 Maeander 
270 Magon 

97 Malya 



263 Margus 
127 Medus 
106 Medusa 

99 Mogrus 

39 Nectar 
135 Neda 
206 Nepenthes 
183 Nereides 
167 Nestus 
269 Neudrus 

29 Nilokeras 
246 Niiosyrtis 

51 Nilus 
188 Nymphaeus 
8 Oceanus 

21 Ochus 
180 Opharus 
149 Orcus 
255 Orontes 
230 Orosines 

24 Oxus 
191 Pactolus 
169 Padargus 

66 Palamnus 
108 Parcae 
274 Peneus 



82 Phasis 
247 Phison 
251 Protonilus 
175 Psychrus 
121 Pyriphlegethc 
220 Rha 
178 Scamander 
223 Sesamus 
174 Simois 

111 Sirenius 
254 Sitacus 
130 Steropes 
196 Styx 

89 Surius 
157 Tartarus 
228 Tedanius 

112 Thermodon 
133 Thyanis 
125 Titan 

72 Tithonius 
208 Triton 
276 Tyndis 
241 Typhon 
110 Ulysses 

56 Uranius 
219 Xanthus 



OASES 



No. 



Name 



No. 



Name 



No. 



Name 



59 Acherusia Palus 
109 Aganippe Fons 
128 Alcyonia 

136 Ammonium 
195 Aponi Fons 
158 Aquae Apollinares 
200 Aquae Calidae 
131 Arachoti Fons 
115 Arduenna 
262 Arethusa Fons 
278 Arsia Silva 
117 Arsine 

96 Astrae Lacus 
134 Augila 
123 Bandusiae Fons 

98 Benacus Lacus 
120 Biblis Fons 
146 Castalia Fons 

65 Ceraunius 
187 Clepsydra Fons 

60 Cyane Fons 
217 Cynia Lacus 



288 Daphne 

124 Ferentinae Lucus 

214 Flevo Lacus 

46 Fons Juventae 

83 Gallinaria Silra 
116 Hercynia Silva 
216 Hesperidum Lacus 
147 Hibe 

58 Hippocrene Fons 
249 Hipponitis Palus 
151 Hypelaeus 

52 Labeatis Lacus 
252 Lacus Ismenius 

50 Lacus Lunae 

78 Lacus Phoenicis 
281 Lausonius Lacus 

75 Lerne 
190 Lucrinus Lacus 
185 Lucus Angitiae 

33 Lucus Feronia 
188 Lucus Maricae 



41 Maeisia Silva 

69 Mapharitis 
118 Mareotis 

53 Meroe 

45 Messeis Fons 
132 Nitriae 
113 Nodus Gordii 
280 Nessonis Lacus 
282 Nuba Lacus 

23 Oxia Palus 
279 Palicorum Lacus 

25 Pallas Lacus 
152 Propontis 
265 Serapium 
248 Sirbonis Lacus 
259 Solis Fons 

85 Solis Lacus 

71 Tithonius Lacus 
126 Trinythios 
154 Trivium Charoutis 
137 Utopia 



mDEX OF NAMES ON THE MAP OF MARS 



ARRANGED NUMERICALLY 



1 Fastigium Aryn 

2 Socratis Promonto- 

rium 

3 Sabaeus Sinus 

4 Deucalionis Regio 

5 Pyrrhae Regio 

6 Noachis 

7 Argyre 

8 Oceanus 

9 Protei Regio 

10 Acesines 

11 Hydriacus 

12 Amphrysus 

13 Garrhuenus 

14 Cestrus 

15 Aurorae Sinus 

16 Caicus 

17 Hipparis 

18 Erannoboas 

19 Dargamanes 

20 Margaritifer Sinus 

21 Ochus 

22 Cantabras 

23 Oxia Palus 

24 Ox us 

25 Pallas Lacus 

26 Dardanus 

27 Tempe 

28 Jam una 

29 Nilokeras 

30 Indus 

31 Hyphasis 

32 Hydaspes 

33 Lucus Feronia 

34 Hydraotes 

35 Hypsas 

36 Ganges 

37 Baetis 

38 Hebe 

39 Nectar 

40 Corax 

41 Maeisia Silra 

42 Chrysas 

43 Agathodaemon 

44 Coprates 

45 Messeis Fens 

46 Fens Juventae 

47 Clitumnus 

48 Ganymede 

49 Chrysorrhoas 

50 Lacus Lunae 

51 Nilus 

52 Labeatis Lacus 

53 Meroe 

54 Amystis 

55 Gatarrhactes 



56 TJranius 

57 Bactrus 

58 Hippocrene Fons 

59 Acherusia Palus 

60 Cyane Fons 

61 Anapus 

62 Artanes 

63 Glaucus 

64 Clodianus 

65 Ceraunius 

66 Palamnus 

67 Fortunae 

68 Iris 

69 Mapharitis 

70 Halys 

71 Tithonius Lacus 

72 Tithonius 

73 Avus 

74 Eosphorus 

75 Lerne 

76 Aesis 

77 Daemon 

78 Lacus Phoenicis 

79 Araxes 

80 Jaxartes 

81 Maeander 

82 Phasis 

83 Gallinaria Silva 

84 Acampsis 

85 Soils Lacus 

86 Bathys 

87 Ambrosia 

88 Ogygis Regio 

89 Surius 

90 Acis 

91 Cyrus 

92 Thyle L 

93 Drahonus 

94 Cayster 

95 Isis 

96 Astrae Lacus 

97 Malva 

98 Benacus Lacus 

99 Mogrus 

100 Aonius Sinus 

101 Herculis Columnae 

102 Hyscus 

103 Memnonia 

104 Erynnis 

105 Gorgon 

106 Medusa 

107 Elison 

108 Parcae 

109 Aganippe Fons 

110 Ulysses' 

111 Sirenius 



112 Thermodon 

113 Nodus Gordii 

114 Eumenides 

115 Arduenna 

116 Hercynia Silva 

117 Arsine 

118 Mareotis 

119 Achana 

120 BJblis Fons 

121 Pyriphlegetlion 

122 Gigas 

123 Bandusiae Fons 

124 Ferentinae Lucus 

125 Titan 

126 Trinythios 

127 Medus 

128 Alcyonia 

129 Brontes 

130 Steropes 

131 Arachoti Fons 

132 Nitriae 

133 Thyanis 

134 Augila 

135 Neda 

136 Ammonium 

137 Utopia 

138 Lucus Maricae 

139 Liris 

140 Eurymedon 

141 Erinaeus 

142 Evenus 

143 Belus 

144 Arges 

145 Gyes 

146 Castalia Fons 

147 Hibe 

148 Axon 

149 Orcus 

150 Erebus 

151 Hypelaeus 

152 Propontis 

153 Hades 

154 Trivium Charontis 

155 Laestrygon 

156 Atax 

157 Tartarus 

158 Aquae ApoUinares 

159 Bautis 

160 Cophen 

161 Antaeus 

162 Axius 

163 Avernus 

164 Cyaneus 

165 Mare Cimmerium 

166 Leontes 

167 Nestus 



222 INDEX OF NAMES ON THE MAP OF MARS 



168 Atlantis 

169 Padargus 

170 Harpasus 

171 Heratemis 

172 Digentia 

173 Mare Sirenum 

174 Simois 

175 Psychrus 

176 Mare Chronium 

177 Thyle II. 

178 Scamander 

179 Gaesus 

180 Opharus 

181 Ilelisson 

182 Chaboras 

183 Nereides 

184 Chretes 

185 Lucus Angitiae 

186 Cerberus 

187 Clepsydra Fons 

188 Nymphaeus 

189 Cambyses 

190 Lucrinus Lacus 

191 Pactolus 

192 Aethiops 

193 Eunostos 

194 Elysium 

195 Aponi Fons 

196 Styx 

197 Galaxias 

198 Boreas 

199 Achelous 

200 Aquae Calidae 

201 Boreosyrtis 

202 Lethes 

203 Amenthes 

204 Astapus 

205 Isidis Regio 

206 Nepenthes 

207 Libya 

208 Triton 



209 Syrtis Parva 

210 Mare Tyrrhenum 

211 Hesperia 

212 Cinyphus 

213 Eurypus 

214 Flevo Lacus 

215 Galaesus 

216 Hesperidum Lacus 

217 Cynia Lacus 

218 Cephissus 

219 Xanthus 

220 Rha 

221 Centrites 

222 Achates 

223 Sesamus 

224 Athesis 

225 Lemuria 

226 Erymanthus 

227 Hylias 

228 Tedanius 

229 Hadriaticum Mare 

230 Orosines 

231 Hippus 

232 Carpis 

233 Syrtis Major 

234 Hyctanis 

235 Dosaron 

236 Japygia 

237 Solis Promontorium 

238 Aeolus 

239 Casuentus 

240 Hammonis Cornu 

241 Typhon 

242 Anubis 

243 Asopus 

244 Arosis 

245 Astaboras 

246 Mlosyrtis 

247 Phison 

248 Sirbonis Lacus 



249 Hipponitis Palus 

250 Arsanias 

251 Protonilus 

252 Lacus Ismenius 

253 Euphrates 

254 Sitacus 

255 Or on tea 

256 Eulaeus 

257 Labotas 

258 Daradax 

259 Solis Fons 

260 Daix 

261 Hiddekel 

262 Arethusa Fons 

263 Margus 

264 Deuteronilus 

265 Serapium 

266 Gihon 

267 Xisuthri 

268 Edom Promontorium 

269 Neudrus 

270 Magon 

271 Acalandrus 

272 Hyllus 

273 Alpheus 

274 Peneus 

275 Hellas 

276 Tyndis 

277 Oenotria 

278 Arsia Silva 

279 Palicorum Lacus 

280 Nessonis Lacus 

281 Lausonius Lacus 

282 Nuba Lacus 
2^3 Mare Icarium 

284 Acheron 

285 Mare Erythraeum 

286 Ophir 

287 Ausonia 

288 Daphne 



INDEX 



Age, of a planet, 206 et seq. ; of 
Mars, 207. 

Air. (See Atmosphere.) 

Aphelion, of Mars' orbit, 12. 

Apsides, line of Martian, 22 ; in- 
fluence on Martian seasons, 23. 

Aqueous vapor, 49 ; boiling 
point of, on Mars, 59 ; speed of 
molecules of, Appendix, Note I. 

Araxes, the, change in shape ac- 
counted for, 161. 

Areography, 92 et seq. 

Atmosphere, importance of, 31 ; 
evidenced by change, 31 ; ab- 
sence on the Moon, 32 ; presence 
on Mars, 32 ; measured on Mars 
by Mr. Douglass, 37 ; method 
of determination of, 38 ; quan- 
tity of, on Mars, 43 ; character- 
istics of, on Mars, 45 ; veiling 
by, 48 ; density of, on Mars, 50, 
52, 75 ; boiling point of water 
in, 59 ; constitution of, 75 ; in 
relation to seeing, 139 ; spectro- 
scopic observations on Martian, 
Appendix, Note HI. 

Ausonia, strait between it and 
HeUas, 115. 

Autumn, length of Martian, 24. 

Axis, tilt of Martian, 22; influ- 
ence on Martian seasons, 23. 

Band, surrounding polar cap, 77 ; 

composition of, 80. 
Beer and Madler, on north polar 

cap, 78. 
Boreas, the, 62. 



Bright spots, on disk, 60, 61; 

variability of, 62. 
Brilliancy, relative, of Mars, 12. 
Brontes, the, 133, 164. 

Calendar, the Martian, 77. 

Canals, 121, 128, 129 et seq. ; 
straightness of, 131 ; breadth of, 
132 ; length of, 133, 134 ; his- 
tory of, 136 ; doubling of, 137 ; 
duplication of, 140, 187 et seq. ; 
catalogue of, 145 ; number of, 
147 ; not natural features, 151, 
153 ; changes in, 155, 157, 161, 
162 ; constitution of, 164, 202 ; 
in dark regions, 97, 148, 171 et 
seq. ; at times invisible, 155 ; 
list of, in dark regions, 173. 

Carbonic acid gas, theory of, as 
related to polar cap, 80 ; char- 
acteristics of, 81 ; objection to 
theory of, 83 ; critical veloc- 
ity of molecules of. Appendix, 
Note I. 

Carbonic dioxide. (See Carbonic 
acid gas.) 

Cassini, rotation of Mars, 21. 

Causeways, 118. 

Ceraunius, relative visibility of, 
183. 

Changes, on disk, 33, 34 ; in tint 
of land areas, 104, 110 et seq., 
118 ; in canals, 155, 157, 161, 
162 ; seasonal and secular, 161 ; 
in spots, 182. 

Cimmerian Sea. (See Mare Cim- 
merium.) 



224 



INDEX 



Clerk-Maxwell, determination of 

molecular speed, 54. 
Climate, of Mars, 49. 
Cloudlessness, of Martian skies, 

45. 
Clouds, 45, 62 ; how formed, 52 ; 

as seen on terminator, 64, 65 ; 

kinds, 68; curious example of, 

seen by Mr. Douglass, 70 et seq. ; 

height of same, 73 ; movement 

of same, 74 ; no trace of veiling 

of surface by, 157. 
Color, of Mars, 121 ; of land areas, 

177. 
Comet-tail peninsulas, 103. 
Cooling, of the Earth, 30; of 

Mars, 30. 
Cracks, theory of the canals as, 

152. 
Critical velocity, defined, 55 ; of 

the Earth, 56, Appendix, Note I.; 

of Mercury, 58, Appendix, Note 

I. ; of Mars, 58, Appendix, Note 

I. ; of Venus, of the Moon, of 

Jupiter, of Saturn, of Uranus, of 

Neptune, of the Sun, Appendix, 

Note I. 
Cyane Fons, relative visibility of, 

183. 

Dardanus, the, double, 196. 
Dark areas, depressions over, 69. 
Day, of Mars, 22. 
Deimos, orbit and size, Appendix, 

Note IV. 
Density, of Mars, 19. 
Denudation, far advanced on 

Mars, 171, 207. 
Depressions, on terminator, 65 ; 

on terminator, over dark areas, 

69. 
Deserts, of Mars, 60, 108. 
Deucalionis Regio, neck between 

it and Fastigium Aryn, 118. 
Development, seasonal, in seas, 

122 ; of canals, 154 et seq. 



Diameter, of Mars, equatorial, 16, 
42 ; polar, 42 ; Appendix, Note II. 

Distance, relative, of Mars from 
Earth, 4, 12. 

Double canals, on map, 106 ; ac- 
count of, 188 et seq. ; appearance 
of, 189; width between, 190; 
manner of doubling, 190, 192. 

Douglass, A. E., measurement of 
diameters, 41 ; cloud observa- 
tions, 70 ; rift in polar cap, 
87 ; observations on the Nectar, 
194. 

Duplication, of canals. (See Gem- 
ination.) 

Earth, ellipticity of the, 25 ; crit- 
cal velocity of the, 56, Appen- 
dix, Note I. 

Eccentricity, of orbit of Mars, 24 ; 
of the Earth, 24. 

Elysium, 60, 61. 

Equator, inclination of Martian, 
to orbit, 77. 

Equinoxes, 77 ; vernal equinox of 
Martian southern hemisphere, 
114 ; autumnal equinox of Mar- 
tian southern hemisphere, 114. 

Eridania, 60. 

Eumenides, length of the, 133; 
oases detected on the, 181. 

Eunostos, the, 62. 

Euphrates, the, shown double, 
106; doubling of, 194, 

Faraday, experiments on carbonic 
acid gas, 81. 

Fastigium Aryn, the, origin of 
Martian longitudes, 95 ; neck be- 
tween it and Deucalionis Regio, 
118. 

Flammarion, Camille, " La Pla- 
n^te Mars," 111. 

Fons Juventae, the, 96, 180, 193. 

Frost, possible effect of, on Mars, 
59, 62. 



INDEX 



225 



Galaxias, the, 62. 

Ganges, the, 98 ; length of, 133 ; 

canals near, 156 ; double, 190, 

193, 194. 
Gases, on the Earth, 50 ; on Mars, 

50 ; effect of, on atmosphere, 51. 
Gemination, of canals, 190 et seq. 
Gigas, oases on the, 182. 
Gihon, name of the, 142. 
Glacial epochs, 24. 
Glaciation cracks, theory of the 

canals as, 152. 
Gorgon, the, 164. 
Gravitation, law of, 10. 
Gravity, on the Earth, 19; on Mars, 

19 ; effect of, on atmosphere, 51. 
Green, N. E., observations at Ma- 
deira, 87 ; map of Mars, 141. 
Gulf of tlie Titans. (See Sims 

Titanum.) 

Hades, the, 194. 

Hammonis Cornu, neck between 

it and Hellas, 119. 
Heat, on Mars, 13; inherent, of 

Mars, 30. 
Hellas, 105 ; strait between it and 

Noachis, 115 ; between it and 

Ausonia, 115 ; neck between it 

and Hammonis Cornu, 119. 
Hesperia, change in, 116, 118. 
Hourglass Sea, the, 21. 
Huyghens, drawing of Mars, 21. 
Hydrogen, speed of molecules of, 

54, Appendix, Note I. ; in free 

state, 56. 

Ice, particles of, in Martian air, 49, 

82. 
Ice-cap. (See Polar cap, and 

South polar cap.) 
Indus, the, first seen, 157. 
Inhabitants, of Mars, 127, 128, 

204 et seq. 
Irregularities, on terminator, not 

mountainous, 66. 



Irrigation, necessity for, 128, 130 ; 

theory of, supported, 172, 202. 
Islands, south temperate chain of, 

115. 

Jupiter, relative orbit and size of, 
5 ; elliptieity of disk of, 25 ; ev- 
idence of atmosphere about, 57 ; 
discovery of satellites of, 140 ; 
critical velocity of. Appendix, 
Note I. 

Kepler, laws of solar system of, 
10. 

Lake of the Sun. (See SoU$ 

Lacus.) 
Lakes, of Mars, 184. 
La Place, theory of primal nebula 

of, 4. 
« La Planfete Mars," 111, 141. 
Libya, 105. 

Life, extra-terrestrial, 5. 
Light, on Mars, 13. 
Limb, of Mars, 46. 
LimbUght, 46. 
Linne, 32. 

Madler, Beer and, on north polar 

cap, 78. 
Map, of Mars, 92 et seq., 141 et 

seq., and at end of Appendix. 
Maraldi, study of polar caps, 22. 
Mare Cimmerium, 120. 
Mare Erythraeum, 120. 
Markings, a peculiarity of the 

Martian, 123, 124 ; bluish-green, 

108, 133; reddish-oehre, 108, 

133. 
Mars, passim. (See particular 

headings.) 
Martian life, 202. 
Martians, as different from men, 

204 ; probability of, 209 et seq. 
Mass, of Mars, how determined, 

16. 



226 



INDEX 



Matter, as common property, 4. 

Memnonia, 60. 

Mereator, map of Mars on projec- 
tion, 143, and after Appendix. 

Mercury, ellipticity of disk of, 25 ; 
evidence of atmosphere about, 
57 ; cusps of, 57 ; critical veloc- 
ity of, 58, Appendix, Note I. 

Meteorites, theory of canals as 
made by, 152. 

Micrometric measures, of diam- 
eters, by Mr. Douglass, 27. 

Mind, universality of, 4. 

Mist, sunrise, 46 ; sunset, 46, 157. 

Mitchell Mountains, 87. 

Molecules, kinetic theory of, 
53 ; speed of, 54, Appendix, 
Note I. 

Moon, cosmically dead, 2; rela- 
tive orbit and size of, 4 ; changes 
on, 82 ; atmosphere of, 57. 

Mountains, 66 ; how detected on 
a planet, 43 ; as seen on termi- 
nator, 48, 69, 167 et seq. 

Names, of planets, 207. 

Nectar, the, 99 ; double, 194. 

Neptune, relative orbit and size 
of, 5 ; probable ellipticity of disk 
of, 25 ; evidence of atmosphere 
about, 57 ; critical velocity of. 
Appendix, Note I. 

Newton, law of gravitation, 10. 

Nice, observatory of, 138. 

Night, on Mars, 19. 

Nitrogen, speed of molecules of, 
57, Appendix, Note I. 

Noachis, strait between it and 
HeUas, 115. 

Nomenclature, of Martian mark- 
ings, 94, 95, 141, 142 ; meaning 
of Schiaparelli's, 142. 

Oases, 131, 176 et seq. ; shape 
of, 178, 187 ; size of, 179 ; onEu- 
menides-Orcus, 181 ; on Pyri- 



phlegethon, 182 ; on Gigas, 182. 

(See Spots.) 
Ophir, 60. 

Opposition, of Mars, 13. 
Orbit, of Mars, 8 ; compared to the 

Earth's, 10 ; eccentricity of, 24. 
Oxygen, speed of molecules of, 53, 

Appendix, Note I. ; in free state, 

57. 

Parabolic velocity, 55. 

Pearl-bearing Gulf, the, 96, 156. 

Peninsulas, comet-tail, 103. 

Perihelion, of orbit of Mars, 11. 

Perrotin, detection of the Phison, 
137, 138 ; confirmation of canals 
of Schiaparelli, 138. 

Phase, of Mars, 19, 37, 46. 

Phasis, the, 161. 

Phison, the, shown double, 106; 
name of, 142 ; double, 190 ; dou- 
bling of, 195. 

Phobos, orbit and size of. Appen- 
dix, Note IV. 

Phoenix Lake, the, 99, 100, 133 ; 
canals near, 162 ; relative con- 
spieuousness of, 183 ; polari- 
seopic observation of, 185. 

Photography, of planet, 93. 

Pickering, Prof. W. H., estimate 
of height of cloud, 71 ; polari- 
scope observations, 80, 185 ; ob- 
servations of rift in polar cap, 
85 ; an open polar sea, 88, 175 ; 
120 ; names by, 141. 

Planets, name of, 1 ; relative orbits 
and sizes of, 4, 5 ; as wandering 
stars, 9 ; as a solar family, 10. 

Polar caps, 22, 33, 76. (See South 
polar cap.) 

Polar flattening, 25, 27 ; amount 
of, 42. 

Polariscope, observations on polar 
sea, 80 ; on so-called seas, 109, 
120 ; on the Solis Lacus and the 
Phoenix Lake, 185. 



INDEX 



227 



Polar sea, 79 et seq., 92, 114, 119. 

Polar snows, relation of, to sur- 
face activity, 113. 

Pole, south, of cold not coincident 
with pole of rotation, 85. 

Poles, of Mars, tilt of, 22. 

Presentation, meaning of, note, 
156. 

Proctor, map of Mars, 141. 

Projections, on terminator of 
Mars, 63, 64. 

Protei Regio, 72. 

Psychic effect, on seeing, 158- 
160. 

Pyriphlegethon, the, oases de- 
tected on, 182, 

Rifts, in south polar cap, 85, 87. 

Rotation, of Mars, time of, 21, 22, 
95, 107. 

Satellites, of Mars, Appendix, 

Note IV. 
Saturn, relative orbit and size of, 

5 ; critical velocity of. Appen- 
dix, Note I. 
Schiaparelli, on tilt of Martian 

poles, 77 ; map of Mars, 94 ; 

first detection of canals, 136 et 

seq. 
Sea of the Sirens, the, 120. 
Seas, of Mars, so called, 96, 107 

et seq., 123, 126, 127 ; variation 

in tint of, 110, 118, 120 ; of the 

Moon, 123. 
Seasons, of Mars, 23 ; length of, 

24 ; phenomenally hot season in 

southern hemisphere of Mars, 

91. 
Seeing, conditions conducive to, 

138, 139. 
Shape, of Mars, 14 ; of oases, 179. 
Sinus Titanum, 101, 134; canals 

near, 156, 182. 
Size, of Mars, 14 ; of oases, 179. 
Snow, on Mars, 33. 
Snow-caps. (See South polar cap.) 



Solar system, size of the, 4, 14, 
15. 

Solis Lacus, 99 ; canals near, 155 ; 
size of, 180 ; polariscope obser- 
vations on, 185 ; bright cause- 
ways in, 194. 

Solstices, of Mars, 77 ; summer 
solstice of southern hemisphere, 
114. 

Southern hemisphere, of Mars, 
seasons in, 24 ; terminator of, 64. 

South polar cap, irradiation from, 
27 ; dwindling of, 33 ; size of, in 
June, 76 ; disappearance of, 79, 
90 ; constitution of, 80, 83, 94 ; 
history of, 84 et seq. ; eccen- 
tricity of, 85 ; rift in, 85, 87 ; 
starlike points in, 86, 87 ; de- 
tached portions of, 89 ; different 
levels of, 89 ; disappearance of, 
90. 

South polar sea, 94. 

South pole, of cold on Mars not 
coincident with geographical 
pole, 85. 

Spectroscope, observations on 
stars, 4 ; observations of atmos- 
phere of Mars by. Appendix III. 

Spots, in bright areas (see Oases) ; 
on border of dark areas, 197 ; as 
terminals to canals, 197 ; in dark 
areas, 198 ; list of, 199. 

Spring, length of, on Mars, 24. 

Stars, Mars as one, 1 ; relative 
distance of, 5. 

Stoney, G. Johnstone, 53. 

Storms, on Mars, 59. 

Straits, in dark areas, 114, 115, 
117, 163, 173. 

Struve, Hermann, 29. 

Summer, length of, on Mars, 24. 

Sun, relative size of, 4 ; effect on 
planet's age, 206. 

Surface, of Mars, features of, 
93. 

Syrtis Major, 20, 105, 119, 141. 



228 



INDEX 



Tempe, 60. 

Terminator, observations on, 48, 

63, 64 ; irregularities on, 63 ; of 

Moon, 169 ; of Mars, 170. 
Tisserand, on polar flattening of 

Mars, 28. 
Titan, the, 102, 184, 164. 
Tithonius Laeus, 99, 181. 
Trivium Charontis, 103, ISS, 

181 ; shape of, 179. 
Twiliglit, on Mars, measured by 

Mr. Douglass, 26. 
Twilight arc, of Mars, 42. 
Typhon, the, double, 195. 

Uranus, relative orbit and size of, 
5 ; ellipticity of disk of, 25 ; evi- 
dence of atmosphere of, 57 ; crit- 
ical velocity of, Appendix, 
Note I. 



Variations, of surface of Mars. 
(See Changes.) 

Vegetation, on Mars, 122, 164 ; vis- 
ibility of, 130, 198. 

Velocity, critical, of planets, Ap- 
pendix, Note I. 

Venus, cloud-covered, 2 ; ellipti- 
city of disk of, 25 ; evidence of 
atmosphere of, 57 ; cusps of, 57 ; 
critical velocity of, Appendix, 
Note I. 

Water, 79, 83, 92 ; necessary to 
life, 76, 127 ; theoretic reflection 
from, 109 ; amount of, on Mars, 
122 ; direction of, when flowing 
from pole, 125 ; as fresh, 175. 

"Weather, on Mars, 58. 

"Winter, length of, on Mars, 24. 

"Worlds, other than our own, 3. 



UEC 131949 



Plate I 



MARS 

SINUS TITANUM 

November, 1894 



LowELi, Observatory 
Flagstaff, A. T. 1S94 



OEC 131949 

















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